You are correct that this has been hashed out many times, but oh... what the heck. I'm waiting for some serious files to transfer and have 10-15 minutes to kill.
You didn't include your expected age at FIRE, nor what taxable accounts and other assets you may have at that point.
There are two strategies you should consider. The first is the backdoor ROTH you mentioned (and since you also have access to a 401(k), you may want to consider a "Mega-backdoor ROTH"). The second is SEPP, which can provide a fair bit of income from your 401(k) accounts.
Beyond that the other option is having some or all of oyur income come from taxbale accounts.
To get a sense of what it might look like in practice, you may need $25k/year in living expense, and you could use $10k/year in ROTH contributions, $8k/year in SEPP payments ($665/mo - your value might be higher or lower), and $7k from taxable accounts.
Given how easy it is to do a conversion later, I'd strongly recommend still maxing out your tax-deferred accounts now to reduce you tax liability and then converting funds later to give yourself a ROTH pipeline. Of course, if you can max our your tax-advantaged accounts and *still* make investments in normal savings, that would be even better ;-D
EDIT; Oops, forgot to include some useful links
SEPP:
http://www.investopedia.com/articles/retirement/02/112602.aspMega-backdoor ROTH:
http://www.madfientist.com/after-tax-contributions/
