When it comes to keeping some of your data on both PCs and mobile devices, outside of Google’s ecosystem of email and office applications, most other apps are ones that sync to both PCs and mobile devices. Some of these sync services have a monthly fee.
I have used Google Docs, Sheet, Slides and Keep from time to time to allow me to get to data via mobile devices. These programs are analogues to Microsoft Word, Excel and PowerPoint, just a good bit less powerful. But, for most needs, they are quite adequate.
If you have never used Google’s office apps, they are available from the apps menu when you are viewing your Gmail. Clicking on the rectangle of dots displays all the apps Google offers. Scroll down a bit to see Docs.
In my Google Docs, I have mostly some prose I started writing on my phone. This allows quick capture of ideas which can be fleshed out later from a PC.
For shorter notes with/without pictures, Google Keep is even simpler to use.
For knowledge management I have been using the Obsidian application, which runs very much the same whether from a PC or a mobile device. I can create or edit a note and have it copied automatically using the Syncthing program. Obsidian has a paid Sync service at $8 a month, which may be easier to setup, but I have not tried it as Syncthing is free.
Obsidian on my PC:
Obsidian on my phone:
These are just suggestions as places to store information to make it available from your PC(s) and your mobile device(s). Of course, you can copy / paste information from these applications to other programs you use on a regular basis, thus making these programs of temporary use.