Upgrade RAM or to get a new unit of iMac?

Figma & Adobe both recommend at least 16GB RAM. Adding RAM to this iMac is easy and inexpensive. You could add 8GB for a mere $17 at OWC. Given the apps you are using, however, I suggest adding at least 16GB (24GB total, for about $40) maybe even more.

And if your iMac indeed has a Fusion drive, you could improve performance by installing Ventura & your apps on a good external USB 3.0 or Thunderbolt 3 SSD and boot from that instead of the Fusion drive.

As far as Ventura is concerned, it's a perfectly good version of macOS and will remain officially supported for at least the next year or two; even after that there is no reason to give up on it unless there are reasons you "must" upgrade to Sequoia or later.

You could invest less than $200 in your current iMac on RAM + SSD and get improved life out of it, or spend $2,500-$5,000 on a new Studio & display.

Well a 2017 is about to become obsolete because with Mac OS Sequoia which is scheduled for release later this year will not run it. Also, upgrading the RAM on a 2017 will not improve speed so I really don't understand your thoughts on why you would want to do this. Without knowing what you anticipate a RAM increase will do it's impossible for us to give you a really good recommendation.

My thoughts are If your 2017 27" either has a Fusion Drive (small SSD + a HD) or a HD then that is the bottleneck on the computer. IF your machine has a Fusion Drive or only a HD then you could upgrade by buying an external SSD which would improve speed. However that will not keep it from being obsolete but it would squeeze some more life out of it.

If you want to future proof then by all means buy a new Mac Mini and a good quality 27" display (Samsung has some excellent displays) and for about $1500 + or - you have an new machine that will keep you future proof for another 7-10 years or so. However if budget is a real concern then add an external SSD to your current computer and for about $200-$400 you have squeezed some more life out if it.

If you don't know how to do an external SSD upgrade it's pretty straight forward, just follow the directions in Use an external SSD as your startup disk … - Apple Community and the SSD I'd recommend is the https://eshop.macsales.com/shop/owc-envoy-pro-sx.

IF you want faster speeds then either the external SSD solution or IMHO invest in a new Mac Mini and external display. Why, because it would be wiser than investing in a 7-8 year old obsolete computer.

That being said it's easy for me to spend your money, it truly is your decision so you need to weigh the pro's and cons of upgrading vs. replacement.

Finally, I'm not sure if you know or not but Apple offers 12 month no interest payments with an Apple Card and if you buy the external display from B&H Photo get the Payboo credit card. If you live in a state that has sales tax the Payboo card will discount the sales tax amount. Where I live (Northern California) that is a 8.25% price deduction. IF you decide to get the MM consider B&H for the Samsung display. Just a thought.

That 1 TB Fusion Drive has only 32 GB of fast SSD storage space, compared to the 128 GB in 1 TB Fusion Drives made before Late 2015.

You can use the Memory tab in Activity Monitor to help determine if you have enough RAM. Keep Activity Monitor open while you do normal work, and keep an eye on the Memory Pressure graph, and the Swap Used. If you see a lot of yellows and reds on the Memory Pressure graph, or the swap used is high, that can be an indication that you do not have enough RAM for what you are trying to do.

That reply has to do with storage and NOT RAM!!!

Yes, that is very expensive. 16GB (2x8GB piece) here in the states is only about $40 USD / RM 188.