Hubby and I just checked in with our financial advisor. We have around $800,000 in 401Ks (his is traditional, mine is a Roth 401k that I started with my last job change. The advisor suggested that we aim for around 30% savings/brokerage accounts 40% in Roths and the balance in a traditional IRA. Fortunately, his employer is implementing a Roth 401k option this year, so we don't have to go the backdoor route, but while we were doing our research, we did find this helpful guide: https://physiciansthrive.com/financial-planning/backdoor-roth-ira/

With the amount of assets you have, it couldn't hurt to have a check-in with a pro from time to time. Total bummer about your 401k having crappy investment options. I've suffered through that in my time, too. Fortunately now I have a bunch of solid funds to choose from!

Good luck!