I would be interested in knowing what model nuc you used to have, but I have noticed in multiple u series 8th gen laptops that either they have heat\power issues or some manufacturers put extra limits in the bios limiting the sustained clock speeds (short boosts are generally fine). This has mainly been on the 8250u and the 8550u (an i5 and i7 CPU respectively), also in form factors with limited\no active cooling (some ultrabooks) or in laptops with poor cooling\power delivery solutions. More recent models have been getting better, but it was a lot of models early on. Also most of my experiences with this were on windows based systems, but I don't think it was just a windows thing.... just that they have a pretty dominant market share.
If you can run an active hardware monitor program while you play and get temp, voltage, and clock speed readings, I would be interested in those when you experience lag.
If you can run an active hardware monitor program while you play and get temp, voltage, and clock speed readings, I would be interested in those when you experience lag.