Regarding the backdoor Roth IRA, I am not entirely clear on why there is an additional tax concern, as both the backdoor Roth IRA (#2 above) and the in-plan Roth conversion (#3 above) involve after-tax contributions. I would have to pay taxes either way, and the tax implications should be the same for both.
I also assume that both Roth conversions are completed on the same day to avoid any interest-related issues. This is all based on my understanding; I haven’t contacted HR yet.
Thanks