A file must be 300 ppi
A file must have bleed
A file must be in cmyk
I am not mocking anyone. You should understand what is important when it is actually important.
Your main problem, in my opinion, is this phrase:
a project that also requires Photoshop
That is a little tiny bit too dam very board.
Let's try to set up some scenarios. Analyzing these will start to show why the myths are actually myths and not rules.
- You have a photo, let's say a 24 Mpx portrait that you need to either adjust, colorize, clean, make transparent or whatever. You probably want to keep the file as the original size, 24 Mpx.
You can totally forget the 300ppi here. You have a 24Mpx file, regardless if you are going to use it later on a magazine cover or a poster.
- You want to make a new digital paint.
If it is small and for an electronic medium, leave it as the final size in px. PPI is meaningless.
If it is for print at a small size, set up your document at the final size at 300ppi, that is with the bleed included. It does not matter if you consider it tedious. If you need it, you need it. If you don't... you don't.
If it is a big size, or you want an illustration regardless the print size, set up your document at a maximum file size of 6000 px on the longest side. It does not matter if it's going to be a 10 mt wall.
Design your illustration thinking about a "safe area" not a bleed. The safe area is only to keep visually important stuff safe if you need to make a crop later. A bleed is only a physical crop, but you could need a composition crop. Just keep that in mind.
Just define your color profiles correctly. Choose a generic CMYK profile to visualize "duller" colors that RGB ones. Keep working at RGB and make some print tests or let the prepress guys handle this.
You only need to setup CMYK values "only" on commercial offset print. Not "digital" print.
You can clearly see when you actually should use 300ppi and when you can not, think about bleed as a crop and forget about cmyk if you do not know if you need it.
If you do not have an idea on what to send, just flatten a copy of the file and deliver a PSD RGB flat file, or export a high-quality JPG file (yes, a JPG file) or a TIF file.
Do not send a PDF file if you do not know what to configure inside the PDF. Only send a PDF file if you have a specific print size or configuration.
In that case, import your image into Illustrator or Indesign and send the PDF from there.