I found that PETG requires a completely different way of approach for the first layer.
With ABS you squish it in, that's for sure, you also squish PLA but a bit less than ABS...
With PETG, almost NONE, LIKE NO SQUISH. I print on PEI sheet and I use a fairly hot first layer and have the tip high enough to just lay it on the bed.
My first layer temp is hot something like 240c if I remember right as I am at work right now, then I drop to I think 230c after that.
My bed temp is about 60c.
Be careful, PETG can stick so well if you get things hot enough and squish too much you will actually pull chunks of bed out when you try to remove it!!!!
The trick to PETG IMO is getting things hot enough that they just lay there and don't get pulled around by the tip.
Think like your pouring a liquid and it does not harden until the tip is away from it.
PETG sticks as it cools, I found when my first layer was stuck too hard I dropped my bed 5c per step till I found my sweet spot for stick.
Takes a little playing around....