I don't have any personal experience to answer your questions, but you may want to join this online forum and ask your question there:
This is a forum for car detailing enthusiasts and professionals. Anytime I have a similar car detailing question, I post there and get lots of very helpful advice from people who really know what they are talking about.
I polished all exterior painted areas of my model 3 with 5" DA (21 mm) except for the following areas where I used 3" DA (12 mm) on my Flex PXE80:
- A to C pillar: to avoid getting polish residue between pillar and glass roof. could also use tape to avoid this issue
- lower portion of front bumper(lip below air intake): probably possible to do with 5" but need lower orbit to avoid hitting plastic air intake. Best to use rotary with no orbit for this area. This area is hardly visible but was applying ceramic coating so wanted to properly prep the surface
- rear trunk/bumper lip: polished with trunk open and did not want to get residue on rubber seal. if you polish with trunk closed then probably no issue with 5" pad
- door jams: was applying ceramic coating to this area so wanted to properly prep. Most people don't bother with this area as it is not visible when doors are closed
Note you will want the side view mirrors folded in when polishing with 5" otherwise will have difficulty getting area closest to windows.
I haven't personally used M210 but I have used Sonax EX 04-06 (orbital version of Perfect Finish) which works well when used with the correct pad for the paint. I would be careful using Perfect Finish (designed for rotary polisher) especially if using a mid to long throw orbital (> 12 mm). You may not get the best finish as this polish is not designed specifically for the side to side motion of DA especially on softer paint like the Tesla model 3.
I used Optimum Hyper Polish (spray format) with Optimum Black Waffle finishing pad on most of the vehicle. Select horizontal areas (trunk lid and rear fender flares) I had to do a heavy polish step (Optimum Intensive Polish with Optimum Orange Waffle medium pad) first to remove some heavy wash induced marks. The best thing about Optimum polishes/compounds is there is virtually no polish residue and it does not stain rubber (no need to tape up any trim areas).