Yes. Your employer provided retirement plan contributions have no impact on your eligibility to do a backdoor Roth. As long as you are eligible to make a non-deductible contribution to a Traditional IRA, you are eligible to do a backdoor Roth. There will be no fees or penalties.
Apologies for my ignorance. How do I know if I’m eligible to make a non-deductible contribution to a traditional IRA? My original concern was that the traditional IRA and 401k “buckets” are treated as one in the same, such that if I’m maxing out the 401k, I can’t pass any additional funds through the Traditional IRA (for purposes of funding the backdoor Roth) without exceeding the yearly max.
The amount in box 1 of your W-2 minus any amount in box 11 is compensation that will support a traditional IRA contribution. Otherwise, the amount that you contribute to a 401(k) or a 457(b) is not a factor in determining the amount that you are eligible to contribute to a traditional IRA. (If you defer all of your available compensation to to the traditional 401(k) and the 457(b) accounts, there would be a zero in box 1 of your W-2.)
There is no limit on the amount that you are eligible to convert to Roth.