I understand, those are two magnificient typefaces. I stopped using Proxima Nova after long years, it’s been my favorite for the longest time. Proxima Nova has a lot of fonts, and if you’re using just a portion of them, it’s maybe worth buying it. I purchased 6 of them a long time ago, never regret it. They score at 25 per font on myfonts.com.
Futura is another incredible Typeface. The first I frantically used in the 90s, and I’m back to it for like 3 years now (thank you Wes Anderson). And for Futura I’m glad I’m on the Adobe Ecosystem. I had bought a few Futura fonts in the 2000s but they weren’t the ones I use today and they weren’t adapted for web use.
I asked because I wanted to provide similar typefaces available on Google Fonts, but PM and Futura are so characteristic that it’s not so easy.
If you are in love with those typefaces and use them so much, and don’t plan to be an Adobe CC subscriber, I recommend you to invest on them. Buy 4 fonts of each each year, and year after year…
Sorry not to be able to provide a better answer