I invest the max tax deductible ( my contribution + firm’s )
You can’t do it as irs has limits . What u can do is ira which is tax deductible and Roth IRA which is after tax
Mega-backdoor Roth IRA if your 401k plan supports it. You can also build your non-retirement investment portfolio.
I’ve never heard of a mega-backdoor Roth IRA. Just the standard backdoor roth of converting a traditional IRA to a Roth. Is there a difference?
You use after-tax contributions to your 401k to fund a Roth IRA. It’s the same rollover mechanism at work but the mega-backdoor allows you to fund your Roth with over $30k per year. https://www.madfientist.com/after-tax-contributions/
No, other tax sheltered options include HSA which has the benefit of being usable in your everyday life for qualified medical expenses.