Should I roll my old 401(k) into an IRA if I still want to do backdoor Roths?

Be careful. Rolling a Traditional 401(k) into a Traditional IRA is often fine for lower fees and broader investment choice, but it dumps pre-tax money into an IRA, which then gets counted by the pro-rata rule and can make future backdoor Roths largely taxable. If backdoor Roths are part of your plan, it's usually better to leave the old 401(k) where it is, roll it into your new employer's plan, or roll only after-tax amounts. Alternatively, convert the whole rolled-over balance to Roth if you can afford the tax. There's no penalty for a direct rollover, and it doesn't count against your annual contribution limit. Confirm rollover rules at irs.gov.