I found that Mozilla VPN uses Mullvad servers and I thought it may be a good way to use Mullvad while supporting Mozilla. Then after further research I found that Mozilla bought an ad firm for ‘privacy-centric-advertising’ and that sounded sus to me. Is it reasonable to suspect that Mozilla VPN may not be as private as Mullvad VPN?
You are reasonable to suspect that. Go with Mullvad who has a proven track record and the 1st party program