Welcome to the community!
Yes, 401K + tIRA/Roth IRA contributions are the best way forward.
As for *converting* (not 'rollover') an IRA into a Roth IRA, yes, a low-income year is the best time to do this because the conversion is a taxable event - tax is due on any gains in the IRA. Afterward, convert $$ annually ($11K+) to Roth, and after 5 years, the initial conversion amount can be withdrawn tax and penalty free. Repeat the larger conversions after you reach FIRE when taxable income should be lower.
Where you hold your tIRA & Roth IRA matters in terms of paying the least for the most return on your ETF purchases. Both Vanguard & Fidelity have brokerage accounts, and their own funds (Vanguard=VTSAX, Fidelity=FSTVX) that can be purchased COMMISSION FREE in a retirement account. Many people are with Vanguard (and Fidelity) for just these reasons, yet most mom-and-pop investors have no idea of this benefit.
And as far as investing in the total-stock-market ETF's, and total-bond-market ETF's, some recommend investing internationally, and in real-estate via REITS. (See
Become a Lazy Landlord with REIT's - BTW... the SNH fund yield is up to 9.03% annually!) Many here have invested in real estate rentals to create a regular income stream as a large part of their FI plan. Rentals, Mortgage Notes, REIT's, etc. Your investment strategy is all up to your risk tolerance. The main point is: pay down those debts first, then save to invest in whatever.
Again, Welcome, and Good luck!