I've been using Mullvad for years. I buy the gift-card type voucher from Amazon, which has a code under a scratch-off type material on the back, & then put the code into the Mullvad app for additional time. No way to tie my Amazon account to that gift card (with a random anonymous code under the scratch off) and then to my Mullvad account. The gift card is also discounted from their normal pricing. According to their blog, they've also recently completed their "migration to RAM-only VPN infrastructure" further assisting with the "no log" policy. I previously used PIA, until Kape Technologies bought them (research "Kape Technologies malware" for my reasoning).

Until somewhat recently, I used to torrent everything. However, Mullvad stopped supporting port forwarding ("PF", which allows you to open a port, so others can connect to you and download content from you. This keeps a healthy "swarm" and helps keep a file seeded past when the original uploader has finished supporting / seeding the torrent. However, this also allowed scumbags to upload / share some horrible content -think children- and Mullvad didn't want to be a part of that, for an obvious reason, as well as others), in addition to some other VPNs dropping PF support. This has caused a big problem for me and many others completing files which are even somewhat old, like not even a year old, and very popular. Additionally, RARBG went down, and I was having trouble finding another website that I liked even somewhat as much.

I use usenet now. Although I don't need a VPN with usenet, I will most likely keep my Mullvad account because of how cheap it is, and how much I like their service and privacy policy.

In regards to Proton email, the base account is free, which I use as my personal account now (with my real name) for family, friends & business. Proton "Mail Plus" is $3.99/Mo., billed on an annual basis (at least that's what I'm seeing). Then, I also have a Tutanota email account (also free) that I use for all other uses (buying stuff, bills, etc.), and I also like their integrated calendar (although I may continue using the Thunderbird calendar). (Edit: I also completed 4 easy "tasks" with Proton, like getting the app, and they upgraded storage from 500MB to 1GB.)

I use the Firefox browser, but I've never used the Mozilla "Firefox Relay" add-on, so not sure if that's a reliable free alternative to your anonaddy. With me splitting up my two email uses, with Proton & Tutanota, I haven't really considered a need for something like Relay or anonaddy. I'll also mention that as far as I know, the VPN that Mozilla/Firefox offers I believe is still Mullvad rebranded.