Agree to disagree. Maybe the 3600 being 65W vs the 3600X being 95W negates that in this scenario, but I think dual tower justifies the cost on most anything with 6 or more cores. I've seen a few tests that show 10C lower temps with a tower cooler with a 3600, even OC'd to 4.2.
That said, I've seen 20C difference between a 6C 3600X and 12C 5900X with the Mugen 5 in the same case (4000X), both running PBO. The Scythe Shuriken or Big Shuriken, Noctua NH-L12S (case-dependent) or NH-D12L would be a good choice if available in OP's market.
OP, if your temps are consistently below 60-63C under load, I would say you're okay for now. But consider one of the coolers I've mentioned if necessary.
I wouldn't bother updating the BIOS unless it's absolutely necessary. Some BIOS updates are known to remove previous support for certain things to "make room" for other things, and it can create an entirely new problem by removing support for something you need it for. MSI actually had
a gaffe where a new update removed Zen 2 support entirely. If it's running, I'd leave it be, but if you want to update it, be sure and keep the BIOS update you're coming from available in case of such issues.
As mentioned, some DIMMs are more stable with DOCP disabled, and it doesn't affect performance horrendously unless it were dropping from like, 4800 to 2133 (if there even is a DIMM like that).
I think timings may have something to do with this in some cases. The 16-18-18-36 timings Asus stated for my Patriot Viper Blackout 4 required manual timings settings, and still caused some stability issues. The BIOS itself popped up its own wonky 20-20-20-40 timings, but I've found they run best at their base 2400 with no DOCP at all. So your new DIMMs may or may not be stable using DOCP on your specific board with the recommended timings.
The only way to find out is to enable DOCP, and see what timings the BIOS tries to use. If they're different from what the board manufacturer recommends, try those recommendations first, then what the BIOS suggests. If neither are stable, I'd just disable DOCP and let it ride. It's not that likely to make that big of a difference.
So you have full functionality of the system now?