Let's say you had one night a week that you could hit an indoor range (25 yard) and limited yourself to one pistol and 100 rounds per visit. Which drills would be of the most benefit for you? Would you perform the same ones week after week or switch them up?

My main goals are to get faster at transitions, general marksmanship, and I'd like to throw in some thinking or problem solving to get the old brain off center too.

100 rounds is enough to do this one twice:

https://pistol-training.com/drills/dot-torture

Grip and stance. If groups are vertical work on stance. Side to side grip. It will help with speed and accuracy.

Before you fire a round, slowly dry fire 10-15 times PERFECTLY. Build perfect muscle memory.

Work in empty mag reloads... you don't always have to start with a full mag. 2 reload 3 for example.

Buy some snap caps and mix em in your mag to work "tap and rack" failures.

"How to get the most out of a 100 round range trip? "

"Dry fire" practice 10-20 minutes, 3-5 times each week.

You can work on fundamentals, that will greatly improve your live fire, through dry fire.

It doesn't need to be super fancy or elaborate, but if you want to go a little crazy with it, you can follow something like this:
https://www.amazon.com/Dry-Fir...VXFc0AYOL&ref=plSrch

Or this:
https://www.amazon.com/Champio...keywords=ben+stoeger

I like this target, I haven't done it timed. Even at 3 yrds I find it hard to stay consistent after the first magazine. My focus starts to fade. It really helps though to make me slow down and hit the dots.

It's a little tougher if you have night sights or other service pistol sights.

They suggest you start with this or do this in the middle of your session and end on a positive note/target.

https://classes.tacticalperfor...com/category/1-dots/