The RO sanders can be a handful... But the older DX93 work great for corners and they come up used for ~$200.
I send my sister mine as she needed to do some corner sanding. I woul dnever send her an RO-## as they act possessed to the beginner and they weigh a lot.
For narrower things you may want to try something like these:
https://www.amazon.com/Mirka-HB-39KIT-Handy-Kit/dp/B00KM0LDHW/ref=sr_1_cc_7?s=aps&ie=UTF8&qid=1508577819&sr=1-7-catcorr&keywords=mirka+sanding+blockThe Mirka screens come in 25-M rolls, so that is 125 sheets/roll for the 8" screen/pad, which is 20 cents/screen. And they last longer than paper.
That little beast uses a light weight Mirka hose and plugs into my Festool vacuum... and if the screen does get clogged, then just remove it and shake it out.
I just got 3 rolls in 180, 240 and 320.
You would probably want 120 or 80 and 120.
If you PM your address I can post an 8-1/2 " piece of each in an envelope.
Even with a machine for a lot of it, the hand sander seems to eat up corners and edges where the machine does not really like to get to.
If it is a machine only, then it will not be too great if it is a round pad job , AND if you are actually trying to sand inside a jam.
So the sander will likely need to be rectangular to be useful.
and the sander will need a vacuum hose, and a vacuum is needed... if there is lead.
The heat gun and scraper, or a rotary paint stripper seems like it is the right approach get the majority of it.
One you are digging out the paint in the pores of the word, then a sander comes into play.
So any brand sander with a vacuum outlet will work...
Therefore... I suggest:
1) mini/midi.
2) Maybe try the hand block approach with the Mirka screens
3) Start seeking used DX93 delta sanders (Craig's list etc), or get a Bosch or Fien or whoever does a dedicated corner sander, rather than having to buy a "do it all" RO sander solely using it for a delta pad sanding function.
4) Look into the "rotary planer" paint strippers.
5) The previously mentioned rectangular Festool sanders seem like the right ones to be considering as ones to use.