Yes, you WANT your money in the ROTH not just because of the tax advantages but other things make it so that I would hihgly encourage filling up your backdoor roth before 1 cent goes into taxable
1) its flexible to take it out, 5 year seasoning rule means you can ladder it out, its not locked up like a 401k.
2) you can invest in tax-inefficent stuff here, and tax-efficent stuff in your taxable account
3) the ROTH is much more protected (say you get sued, its pretty untouchable) as its a retirement account
4) getting your assets into ROTH and 401k as much as possible allows you to pass for poor when it comes time for applying for anything that is means tested. Im thinking specifically FAFSA Hacking, money in the bank and after-tax accounts are counted against you, but NOT your ROTH and 401k!
5) you don't generate a big pile of tax paperwork by buying and selling inside your ROTH. Matter of fact you don't file any tax paperwork on your ROTH until you take money out.
I park my after tax 401k in money market until it gets backdoored into the roth, then it gets properly invested (youll pay tax on about $100-200 in gains from that, no big deal)
I can make as many withdrawals as I want, so I could theoretically do the backdooring every paycheck, but the paperwork (it must be done by snail mail) is a hassle and takes almost 2 weeks to process, so my general procedure is to:
1) fill up ROTHs in winter
2) keep the pre tax 401k steady through the year, because in order to get the most matching you must not max it out until paycheck #26.
3) save a little bit of 'float' money in the spring.
4) in the summer I go full out contributing to the after tax (nearly the rest of my paycheck) as my expenses in the summer are lower (no preschool, no family travel, my big semi annual and annual expenses hit, like property tax and HOI avoid summer)
5) halfway I do one rollover, and another rollover at the end, the whole process typically takes 9-10 biweekly paychecks to completely fill up the backdoor space.
6) any money in fall goes into after tax (ie all other tax advantaged accounts exhausted, even my HSA... I treat it solely as an investment vehicle, not for medical expenses!)