Will more RAM help my iMac run faster?

Adding memory will generally not speed up your computer however it will keep it from slowing down as more apps use memory and you get near your maximum amount of ram your computer will starting swapping memory to the hard disk. The hard disk is slower than memory so your computer slows down. Put in simple terms.

If speeding up your computer is the goal of your question i offer the following info.

Generally its impractical to add a faster cpu.

But...

Do you have a hard drive or a solid state drive in your computer.

If you have a hard drive adding a solid state drive (SSD Drive) will greatly increase speed.

If you already have a solid state drive not much more you can do.

Post back if there if you are interested in adding a this type of drive as there are some things to know before installing this type of drive depending on the brand of drive and the operating system you are using. Perhaps start a new question on the topic rather than extending this one.

Add more RAM does help.

For the uses you seem to be involved with, 8 GB should be enough.

When you get to a point where your getting beach balling and otherwise sluggish

performance, open Applications->Utilities->Activity Monitor and check CPU and

Memory usage. In particular on memory usage, check the number of Page Outs.

This is a measure of how often memory swapping is being done due to low RAM.

If this number is zero or very small, then RAM is not your problem.

FWIW, Chrome seems to be quite a memory hog.

More slowness issues are related to third-party programs than lack of RAM when one has as much as you. The following are much more likely suspects in slowness issues like you have described:

1) Are you running any anti-virus/internet security applications?

2) Are you running any "cleaning/tune-up/optimizations" applications?

3) Any peer-to-peer or torrent downloading software?

4) Any third-party disk backup software that came bundled with an external hard drive?

5) Any online backup scheme other than iCloud (Carbonite; GoogleDrive; MS One Drive)?

6) Did your financial institution ask you to install Trusteer EndPoint Protection (also known as Trusteer Rapport)?

good points Allan jones

Download and run Etrecheck. Copy and paste the results into your reply. Etrecheck is a diagnostic tool that was developed by one of the most respected users here (and recommended by Apple Support personnel) in the ASC to provide a snapshot of the system and help identify the more obvious culprits that can adversely affect a Mac's performance.