Is 16GB of unified memory enough to support 8 different chrome profiles with multiple tabs open, 2-3 apps and while on facetime?

All current iMacs come with 16GB RAM as the base amount. The untold message is that 16GB is now the minimum the Mac needs to run. Yes, you can install apps & run them and that will probably be ok for most general purposes and users.

But you said you want to buy something that will last for the next 10 years. And you are concerned about the demand put on the system by Chrome (which is known to gobble up system resources) as well as run multiple apps simultaneously including videos & Facetime.

I suggest that in your case it would be wise to consider at least 24GB RAM, even go all the way to 32GB RAM in order to future proof your purchase. The new iMacs cannot be upgraded after purchase, so you need to make that decision now.

I also suggest getting an iMac with 1TB SSD instead of 2TB. Invest the difference in a good external SSD instead of putting all your eggs in a single internal SSD.

At present, a new iMac with 24GB RAM + 1TB SSD comes in at $1,899. With 32GB RAM + 1TB SSD it's $2,299.

I actually concur with both rkaufmann87 & MartinR's suggestions ... but since I have been a Mac mini user since the 2008 models, I have a lot of experience with them. As such, I tend to recommend the minis over the iMacs.

The entry level mini with 32 GB RAM & 2 TB SSD comes in around $1799 (USD). As rkaufmann87 has already mentioned you can get a wide selection of monitors to suit your needs. I currently use a 27" Dell 4K monitor with my 2023 M2 Pro Mac mini. The mini, itself takes very little desk space so that is a plus should space be a premium.

Regardless of what you end up going with, Apple has a 14-day return policy should you have any initial regrets.

... but back to your original question, I would strongly suggest going with 32 GB RAM option. For the SSD, I tend to agree with MartinR on going with a 1 TB model (don't go lower), and then, consider getting external storage if you really need the additional space.

I agree with those recommending the Mac Mini. I recently purchased a Mac Mini M4 with 16 GB of RAM and 1 TB of storage and a 32" 4K LG monitor for under $1500. I run Safari with 39 windows open in tabs with no problem. With Safari (40 windows open), Activity Monitor, Mail and Photoshop Elements open the memory pressure looks like this:

Since you're using Chrome, which is a know resource hog and mines your data, you might want to go with 24 GB of RAM or another browser. With the Mini and Sequoia Safari is most capable. If you don't like Safari Brave or Firefox are excellent alternatives and much more secure than Chrome. (Personally I don't allow any Google software on my Mac.).

Also if the budget permits get 2 TB of storage as it'll be blazingly fast accessing applications and files.

To be honest, I would get a new Mac mini rather than an iMac. All you will need is a new external display (they start at <$100) but a nice one expect about $300. You can use the old Mac keyboard and mouse. If you get 2TB of storage and spend $300 on a new display total outlay is $1699. If you get a similarly equipped iMac the cost is $2299 so you can save $600 or over 20%. In addition, if you are in the USA, Apple offers 12 month same as cash financing. So you don't have to load up a credit card or deplete savings. Just pay about $150 month and the MM will be paid off in 12 months. You can use the $600 for whatever you want, for example get a new external HD for your Time Machine backups.