One thing I would add is determine your average riding outside gear ratio between chainrings and cogs that you use most often. Assuming you are testing/training in ERG mode, use that ratio and try to match it on your indoor setup for the ramp test and training in general. Also, if your focus is MTB/Gravel, use the smaller chainring. If you are more of Roadie, use the larger chain ring.
You can read more why at this thread: Big vs Small Chainring - Same Power (ERG Mode Gearing)
Basically, with ERG mode, you can really skew your results if your gearing is inconsistent with what you would do outside due to the inertia effect of big vs small ring. When I first started TR, I changed to small cog/big ring on my 2nd rampt test and got a huge unrealistic bump in FTP result. When I went back to a ratio that matched MTB better, I started failing workouts left and right. Changed back to small cog/big ring from the test and I could finish workouts again, but first MTB race I lost all my punch up climbs and low cadence/low gear ratio fitness. I could ride forever and noticed considerable gains on road bike, but I wanted to improve for MTB races. Following my advice above in first paragraph has really been a game changer for me. I got back/improving my punch up climbs and low cadence/low gear ratio fitness for MTB races now.
Bottom line - align with your cycling focus and match the ramp test/ gear ratio. The test is just an assessment to make the training work you hard enough, but not too hard to fail workouts. I know for a fact I can switch to small cog/big ring right now and get an instant 20+ bump in a FTP test. But the problem is that I will never get even close to that ratio in MTB races, and the lower cadence needed in MTB is much harder to keep going when you don’t have as much inertia help from the bigger chainring. So if I train at that ratio, I wont see the desired gains for MTB.
Hope that helps - Just don’t want you to make the same mistake I did.