Be sure to validate the x and y (eastings and northings, typically) separately from the z (elevation) regarding feet, surveyfeet, and meters. For some reason, I've seen lots of xy in meters and z in feet. I use https://mapper.acme.com/
with the options set to UTM to see the UTM x-y value of the crosshairs (in the middle of the browser window). In the US, you can use the Topo map layer to view 24K, 100K, and 250K map scales. The 24K (zoomed all the way in) are feet elevations, the 100K are meters elevations, and the 250K are back to feet elevations.
If your eastings and northings are both 7-digits, that's an indication they're in feet, but it isn't perfect because west in the "UTM wedge" the values will be 6 digits. UTM northings in meters max out at about 10,000,000m, and in the USA are usually in the 3-5 million range. If you see really big northings, like 9-16 million range, that's probably feet. But a lot of state projections have weird false eastings and northings that give them random values where the only thing you can say is "It doesn't match the expected coordinates for UTM in meters".
It's good to run lasinfo.exe on a file to see any embedded metadata and to see the x y z value ranges, as well as other cool stuff like how many returns and what classifications they have.
lasinfo -i filename.laz -otxt -cd
but leave off the -cd if you have a lot of files or if you're in a hurry. It calculates point density (points per square meter) as well as post spacing. Post spacing is a weird parameter. I think a post spacing of 4 means 1 return in 16 square meters.