Rachel Johnson

Good question and yeah there's no hard rule that says you MUST use phonetics every single transmission, it's more situational. On a clear local repeater where everyone knows you, saying your call straight is totally fine. Where phonetics really matter is when conditions are rough — like on HF when there's QSB or QRM and the other station is struggling to copy you. The NATO alphabet exists specifically because those words were chosen to sound distinct even through noise and different accents, which is why using your own made-up ones can backfire. "Apple" and "Alpha" don't sound that different through static but "Alpha" versus something like "Able" which some guys use from the old phonetic alphabet can cause confusion. Just practice the NATO ones until they're automatic and use them whenever there's any doubt the other op might miss a letter.

congrats man. what radio are you running if you dont mind me asking, i just passed my tech too and im still trying to decide between a few handhelds before i make my first transmission

yeah the window system is still how it works, you basically got it right. when you apply for a vanity call there's a 30 day filing window and if nobody else applies for the same call during that window you get it, pretty straightforward. but if someone else also applies for that same call during the window then it comes down to license class and then years licensed, so an Extra with 20 years would beat out a Tech who just got their ticket. that part stings a little if youre going after a popular call.
as for your grandfathers call — that actually might work in your favor depending on how long ago he let it lapse. calls that belonged to a deceased family member can sometimes be applied for and there used to be a preference for that situation, though the exact rules have changed a bit over the years so id double check the current Part 97 language or look at the ARRL vanity call page, they usually keep that updated pretty well. its definitely not impossible though. good luck, hope you get it.

pi zero is probably overkill for relay switching yeah but if you ever want to add a web interface to control things remotely or log switch events it starts making more sense. i run a pi zero W for my rotor controller and being able to just pull up a webpage on my phone is pretty handy. that said the latency when it boots is annoying and if power goes out you gotta be careful with the SD card corruption thing — learned that one the hard way a few times.