Here would be my NON legal advise.
If you have questionable pistols take the lower off and store them that way. When you go to the range, put it together shoot it then take it apart. You can’t be in trouble with the law if it’s taken apart. I would also say transport the weapon to the range taken apart.
Tax stamps for SBR are good if you never plan on leaving your state. However if you want travel, you have to do paperwork with the ATF to let the ATF know what state your SPR is in. When I used a road trip I’d be in 13 different states on a trip I would have to do a form for every state for my road trip and it was a huge pain in the ass.