I had started to answer this post earlier and got tied up.
#1 I would say drop using DC. Just because you can specifically run the limited items you listed- no, long term, Lionel engines, cars, and many operating accessories need and require AC and some can be damaged by DC. To say what you have now is all you will ever have or buy is not a good outlook on the hobby. Again, the fact is, AC is the standard, DC is starter sets and limited items, eventually something will likely require AC in the big picture.
#2 Your fastrack switches, while they technically work with DC, do not fully function and at least one color of the indicator light will not work on the remote controls. This is because the fastrack RSC/Lights format is +5 or -5V and with DC you are missing one of the voltages. Again, they work, just not 100% as intended.
#3 Your base 3 comment bothers me. Unless you have or are also getting a CAB1L physical remote, or happen to get a CAB2 remote, to me that's spending $500 on an item I don't think you really based on your comment understand. If you only buy the CAB3 base, and have to use an app- that app is bluetooth already talking directly to the engine.
If you want to give Lionel money- that's fine, but again, just what you said,
Mike: Thanks for your quick response. Plan is to run 2-Lionchief locos. One existing Santa Fe FT starter set (loco plus 3-cars). Later, plan to add a Lionchief steam loco with 3-4 cars (post war), or starter set (which may have some bells and whistles). Switches will initially be operated manually, but may add blue tooth thru the Base 3. Hope this helps, or helps me??
Again, you are buying Lionchief locos- starter sets. I get the impression you read marketing wrong or do not really understand the Base 3 function.