TLDW:
bare screen 1% wobble.
tempered glass 80% wobble.
matte film 10% wobble.

00:00 intro
01:03 Bare screen
01:40 Installing ESR Tempered Glass
02:07 Drawing on ESR Tempered Glass
03:22 Installing Bellemond Matte Film
03:49 Drawing on Bellemond Matte Film
06:44 Discussing Bellemond Matte Film's issues


Digital pens and pencils on many tablets sometimes show a jitter or wobble, a very small wiggle, when making diagonal lines. Wacom and Apple are two of the best at reducing it when using default hardware. Adding any screen protector exacerbates the wobble.

Solutions:
Don't use tempered glass.
Use procreate streamline and stabilization.
If you don't want matte, find a PET film protector that isn't matte.
Don't use any screen protector at all.

Hardware used:
Ipad Pro 2021 M1 12.9" and apple pencil 2
Head shots filmed with Lumix GF3
Lines filmed in 4k with OnePlus6
Audio-Technica AT 2020USB