Does the WINDBAR wattage calculator include Geek Bar Pulse X ohms?

No. Those ohms are unknown here. Type the WINDBAR insert.

What if I only know a Geek Bar 5000 listing and not my coil print?

Stop. Ohms unknown, watts unknown.

Can I use 1.8 Ω because SPECTRUM publishes it?

Only if your insert says 1.8 Ω.

Does 4.4 V and 1 Ω mean I should fire 19.36 W?

No. That is educational math. The insert wins.

What should I open after this page?

The WINDBAR wattage calculator, then D91 or SPECTRUM on this site. Do not leave for another calculator.