If you have access to a Mac, use the Apple AAC encoder. It will give you better results than libfdk_aac, which itself is much better than the ffmpeg built-in aac encoder.

In general, I’d say it’s good enough. i5 might have more cores if you need them, but then i7 only gets you slightly higher frequency, which may not be worth the price.

Here is a thread with 4th July deals. On that forum you can often find deals for cheap, low-spec VPS.

live plex transcoding

If you need this, the most cost-efficient way is probably to get an Intel CPU with an integrated GPU that supports QuickSync (all recent ones do) and pay for the lifetime Plex Pass. In the long run, it’s cheaper than getting a beefier CPU, let alone a dedicated GPU, just for transcoding.