Is 8 GB ram adequate for my usage?

It depends on various variabilities.

Which browser to you use? For ex. Chrome is known to be a far more RAM user then Safari.

My daily driver is the model you want to upgrade to (M1, 8/256), and I throw at it basically the same stuff you do (Safari with few tabs always open, iTunes or Spotify always open, YT, movies, PDFs (via Preview), Apple Notes, Telegram, Apple Mail, MS Office, ...). I can tell you that it can handle more than that without problems.

From my point of view, you're going to see a difference between your old 2015 iMac and the newer M1, because of the far more superior CPU unit. The 8GB, with the usage you describe, aren't going to be a problem for that amount of RAM.

I read recently that the new Apple silicone processor s , M2, in your case are “closer” to the RAM. I am sure that’s is in relations to physics if not literal “Number of contacts between the chips themselves. But any way the idea is that the Ram and CPU talk to each other faster now. And maybe the RAM it self is faster, not sure about that one.

Regardless, the point was that for everyday multitasking with things like web browsing, email, word processing spreadsheets, browsing your picture album works as good in 8gb Apple Silicon Mac as 16gb Intel Mac.

I have the 2015 16gb fusion and just went to the silicon 8gb. The 2015 was slowing down too much, presumably with all the new OS features, but the new one is back to normal speed; many pages open on Safari (although I typically shut down the one Google shared photo album from another family member, because Safari tells me it is a memory hog), Word running, Photos almost always open, emails checking constantly , iMessage and even screen sharing running few times. Too early to tell completely hands on, but I am happy for now.

If I were doing a lot of long video editing, like 30 minute clips or more I’d get the extra RAM. I’ve done one or two in the past without though without much Ram, just takes a bit longer.

I don't think you'll see a performance hit with half the RAM because the Apple Silicon chip is much more capable than the Intel CPU in the old Mac and because of the way the new Macs are built to access the RAM as integrated on the logic board.

My personal choice would not be 8GB RAM. That's what I consider to be the bare minimum acceptable.

Yes, it will work today, but consider that things change and RAM requirements trend upward over time. Apps and OSs released tomorrow may perform best with or even require more than 8GB.

I would buy a model with a minimum of 16GB RAM. Future-proof your purchase.

I agree with the position that 8GB, while acceptable as the bare minimum, is not the way to go. In fact, there was another poster in this same section that went from an older 16GB iMac to a new 8GB iMac, and didn't see much of a performance boost. And there are apps that want more than 8GB (Chrome being RAM hungry, for example...and Adobe recommending 16GB or more for their apps). Another consideration is that you'd be purchasing a Mac that's already 4 years old. Apple's support for it will end in the next 3-4 years.

Just my $0.02 worth.

I don't think you'll see a performance hit with half the RAM because the Apple Silicon chip is much more capable than the Intel CPU in the old Mac and because of the way the new Macs are built to access the RAM as integrated on the logic board.

My personal choice would not be 8GB RAM. That's what I consider to be the bare minimum acceptable.

Yes, it will work today, but consider that things change and RAM requirements trend upward over time. Apps and OSs released tomorrow may perform best with or even require more than 8GB.

I would buy a model with a minimum of 16GB RAM. Future-proof your purchase.

...to a used 2020 iMac M1 8GB RAM 256gb ssd

The 256GB SSD causes me far more heartburn than 8GB RAM. Apple overhauled RAM management in 2013 making it much more likely to run well with base levels of RAM.

256GB on a boot volume may seem fine now, but I've seen too many posts here where users opted for the smallest SSD capacity only to later find they did not have enough free space to do system updates.

Another thing with M-series iMacs: if this this the entry level version that has only TWO USB ports, walk away. That is a big limitation in my eyes. At some point, you must charge the mouse and keyboard; that uses a port. So do external backup hard drives, mandatory for computers like the M-series Macs with non-removable storage. Two ports are not enough IMHO.

If looking for a discounted Mac, best to only use Apple's on-line store and its certified refurbished devices:

Refurbished Mac Deals - Apple

I'd estimate our family has bought 12-15 refunds directly from Apple. Every one gave long and reliable service

For this 8GB should work fine.

Where are you getting the "used" iMac? If not from Apple or OWC (MacSales.com) I would seriously consider not getting it but get one from the two sources I mentioned previously. Too many users have posted here that after getting from eBay, Amazon, Craig's List or from individuals they unit was not prepared correctly and they ended up with an expensive door stop if they didn't have return capability. Just some food for thought.

If you get it from Apple's refurbished site it will have a "new iMac" warranty.

If the 2020 unit is from a reliable source where you can take it back if there's a problem you'll be able to add memory if you find the 8 GB is not enough. It's the last model Apple offered where the RAM can be upgraded after purchase.