"If I convert my 401k IRA to a 401k Roth, let's say a portion of it - 50k (would pay the taxes outside of the plan) , can I still contribute to a regular Roth IRA outside of my plan?"
Maybe, maybe not. Unlike a Roth conversion from a traditional IRA, the taxable amount of an In-plan Roth Rollover is included in the MAGI for determining how much you are eligible to contribute to a Roth IRA. If the additional $50k of MAGI moves your MAGI above the MAGI that makes you no longer eligible to contribute to a Roth IRA, you would not be able to make a Roth IRA contribution that you otherwise would have been eligible to make.
