Just to be clear, the $19500 limit applies to all contributions together. You can't contribute $19500 each to both before- and after-tax. But you can split it up however you like.
I had already accumulated a large before-tax 401(k) before my employer offered the Roth option. I switched over, and now I have some of each. I presently contribute the max to the after-tax option only.
I'm currently "front-loading" because I expect to FIRE this year. But I'm aware of what MetalCap pointed out: if your employer match is at the max, then you're getting less, since they won't match for those pay periods in which you can't make any more contributions.
By the way, employer matches are always "before-tax", even if your own contributions are "after-tax".
If you really want to go hardcore, you should also contribute $6k to a separate Roth IRA of your own. I'm turning 50 this year, so I also get to do "catch-up" contributions. My take-home pay is like $50 a month.