I prefer a thick sheaf of used, greasy bills in a fat little envelope.

Can’t be that bad since these dang trees look to be on average 3-5” thick.

And the carpet thickness must be less than 3mm, otherwise the laminate flooring is easy towarp when people walk on it as the flooring will sink and change too much when people step on it and the carpet is too thick.

If the thickness between the old and new is an issue, slight shims where replaced resolves that quickly.The dips or waves in the roof (ext picture) are generally from the rafters that are uneven across the span. 

I am thick skinned

My house is built in 1925 with thick beautiful hardwood floors all through out, I was looking to hire a professional but it is so expensive when I can rent the machine for about 50$ a day.

How about carpet with a thick underlay?

Yup that's right it was 3 inches thick of flooring...before you even got to the sub floor.

It had some nice old hardwood with thick trim and base boards.

I did have the advantage of having thick plaster walls with good paint coverage, and tall baseboards, that prevented the kind of soak-in that you find with drywall paper.