Congratulations on the new bike.  I got one too.

I use a cable lock and padlock.  The cable is to prevent people from lifting the whole bike and putting it in a truck.  I lock the helmet with a cable too. I am just trying to frustrate opportunistic thieves and people who don't think clearly. Once somebody has your bike, a power tool will break any lock.  Also, after breaking the lock, the power tool can be returned to the store for a refund.  So anyone who is somewhat resourceful and has no morals has access to lock breaking device.

I stay away from high risk areas.

I park near the front door of the business so everyone can see and never leave the bike more than 15 minutes for a "to go" cup of coffee and a bathroom break.

I keep the battery on the bike.  I take the phone.  It is all a risk, of course.  But I think it is too much trouble to carry the battery with me everywhere.  And then if you are concerned the seat, the iPhone mount, can be stolen too. It is so much trouble to carry a battery, pump, repair kit, helmet with you just to go to the bathroom or to buy some liquid. And then there is the quick-release front wheel. which can be removed in 15 seconds.  If I am that concerned, I just drive.  I just don't see the ebike as a viable commuting tool or a tool for running errands.

The downside of any security system is that it is heavy and it is with you 100% of the time.  If you carry it you need to strap it down or else it just bangs on each other or the rack and destroys it.  Most of the time I carry nothing but the phone and the tubes are slimed. Sometimes I carry a cable and padlock for bathroom break. I plan on calling Uber or a taxi if there are problems.  When I used to commute on a regular bike, I kept the lock at work locked to the bike stand.  That way, I don't have to carry it. Just sharing another way to live.

I measured - the lowest height for the seat for a Rad Mini Step Thru is 30.5 inches.  I think it is one of the lowest around.

The seat post does not go down all the way.  I think if you are willing to cut one inch off the bottom of the seat post, it will go down another half inch and you can make the seat height to be 30 inches off the ground.  Seat post, not the seat tube!!!  Don't modify the frame!!  This is my guess and I don't take any responsibility for safety if you cut the seat post.  Also, I have not done it so I do not actually know if this would work.  Do it at your own risk.

My seat is usually higher.  But - it is nice to set it low in the beginning especially if the rider had not ridden a bicycle for a long time.

If I had to do it again, I would buy the mini again because it is already huge compared to my non electric 700c road bike.  E bikes are huge - even the mini.  With a 65 pound bike, I like to keep the weight closer to the ground like in a mini.  I think if a person is not confident and comfortable on a bike, they would not ride it much after the novelty drops off.  So while a person may be able to handle a bigger bike and the bigger bike may fit when riding. The difficulties when dismounted or during a sudden stop may make someone uncomfortable.

I think the mini step thru is a great bike and it is so cheap.  With the money saved, you can buy a 2nd battery - you don't have to but you can think of it that way.  A mini with 2 batteries will beat the rad city step thru in range and power - because you can use assist level 5 for many many miles.  That was my plan all along. But now that I have the bike, I don't think a 2nd battery is needed for my type of riding.  So maybe don't buy the second battery yet.  But knowing what I just said may give you some comfort.

Also get advice from other people.  It is your decision.

I am wondering. How does a Rad Rover 6 Plus or any "full-sized wheel bike" compare to a Rad Mini in hill climbing? The way I see it, a Rad Mini, because of the smaller wheel, will have an advantage over the Rad Rover 6 Plus in hill climbing since the hubs are probably not that much different. 

Or to put it another way, rated purely on hill climbing, a 750 watt 20 inch wheel bike should beat any 750 watt bigger wheel bike unless there is a significant difference in gear ratio. In this case, I think all Rad Power Bikes are 5:1 gear ratio.

<deleted my comments> I think you have a typo in one location.  I see you are asking about protection for the "Rad Mini" and not the Mini ST.

Sharing my discovery. I was able to connect my Burley Trailer using the old style hitch to my Rad Mini ST rack. No modifications needed.  All the parts were standard and not altered at all.  Even the safety strap could be connected. Took me about 10 min to figure out but it can be done.

Of course, I am not endorsing this and you take your own risks doing this.  I am not carrying a child in the trailer.  This is my cargo hauler.

"Choking the electron" is real.

I installed a new Rad rear rack onto my Rad Mini ST and I also observed that tightly coiling the wire around the connector and tightly zip-tying the bundle together contributes to error 25 - that is, "choking the electron."  Maybe the connection is tenuous to begin with and any additional strain on the connector bends it just enough to ruin the connection.  The problem goes away when you disconnect and reconnect the cable a few times.  After a few rides, Error 25 comes back.  I've requested a new electric cable (for extending the brake light from the original mounting position to the rear of the rear rack) from Rad and I hope that solves the problem.

Just my humble opinion.  You can take it or leave it.  Maybe you have experience so you don't need this.

I suggest a nice dropcloth so you can put it together in the warmth of your family room with strong lighting.  A warm room - and maybe all the time in the world - will make for a nicer setup for you.  It should be an enjoyable time, don't rush, enjoy yourself.

It was the first time for me of mounting a wheel with a disc brake.  I suggest getting help lifting the bike up so you can take your time slowly putting on the front wheel so as not to bend the disc of the disc brakes. I don't even know if it is possible to bend the disc, it was the first time for me but it sure helped that I took it easy and slow.

Nice diagonal clippers or strong scissors for cutting the zip chords.  Take your time.  Don't scratch up the bike.

You will also need a bike tire pump if you don't have one.

I think the brakes will rub a bit and the bike wheels will not be as free spinning as a regular bike.  This is just my comments - and I am not taking responsiblity for it.  If it is just making some small noise just live with it and ride 50 miles, the cable will loosen and you will have to adjust the brakes again.  I think the wheels will be as free spinning as a motorcycle wheel or a moped wheel.  It will not be as free spinning as a bicycle wheel.

They left it nicely next to the door of the garage.  No bell ringing or any notification.

I am just fantasying about building my own rear wheel from a rim, motor, and spokes.  Is the rear wheel on the Rad Mini Step Through offset to accommodate the chainring like in a traditional bicycle?

Also, do you have a recommendation for a wheel truing stand?

Thanks for your time and help.