Don't get hung up/paralyzed into doing nothing for fear that something slightly better might be available if you did hundreds of hours of research. The most important thing is to get started, IMO.
Just to be clear. The Mega backdoor Roth requires a 401k that allows After-Tax Contributions. Most won't let you do that. Their software will say "that contribution percentage you have selected will result in more than $18k/year in contributions and that isn't allowed" or you'll get to the end of the year and they'll just refund you the extra contributions. Which also doesn't help you.
Don't get hung up/paralyzed into doing nothing for fear that something slightly better might be available if you did hundreds of hours of research. The most important thing is to get started, IMO.