re: Roth 402G limits

The 402g limit isn't a Roth thing it's a Roth or Pretax thing - limit is 23k this year. If you go over, it sounds like it rolls to your after-tax account.

If you're over 50, you also get a $7,500 catch-up, but this doesn't count to your 402g limit.

402g is $23,000 (either pre-tax or Roth)
Catch-up is $7,500
Company contribution is "X"
Total Maximum is $69,000

69,000 - 23,000 - 7,500 (if applicable) - X = Maximum After-Tax Contribution

Some companies cap your contribution to say 15% and that is what it is. You'll have to check what this looks like for you by calling Fidelity.