Where to store (Adobe Project Files, Images, Videos etc..)?

Hint: Don't waste space by installing Adobe's apps on your 1TB drive. Your Operating System will likely never hit the 250GB mark and all Adobe apps are relatively small in size, so better install everything software-related on that one.

Get a bigger boot drive and don't customize the Creative Cloud install location. That's a really bad idea. For all 3rd party effects, scripts and updates to work reliably you cannot fiddle with the install of After Effects or Premiere Pro. You are just asking for trouble. Unless the second drive on the same buss inside your machine it is going to be up to 10X slower

The transfer speed is actually more critical than the drive speed. You can plug an SSD into a Thunderbolt port or USBC port using the wrong cable and have the transfer speed drop from 40 Gbps to under 2. You can run into the same problem with SATA ports and cables. You have to use the best materials available.

You should consider using a Raid 0 or Raid 10 for footage and project files. Storing footage and project files on a single drive is not ever a good idea. A mirrored raid gives you automatic backup.

My setup = 5 drive Raid 10 - 2X drives mirrored and 1 that is an automatic backup drive should one fail. I can pop any single drive out at any time and drop in a new unformatted drive that will fill up with data. Then I put the backup in a safe. I never spend a minute backing up or making archival copies because the Raid system takes care of it.

At the very least you should put your working footage and save the project files on a 2 drive Raid 0 system so you have mirrored copies at all times.

The media cache is also best on your boot drive if you have space because there is nothing faster. My boot drives are almost 10X faster than any external drive you can get.

The only backup that I run is a backup of my system drive on a bootable disk. A new copy is made every two weeks and I always verify that I can boot to the backup drive before I run software updates. The result of this kind of planning is Zero downtime because of a drive failure in the last 8 years. If an update kills something all it takes to get me back in business is plugging in the system copy, booting to that drive. That usually takes less than five minutes. When things calm down I can either troubleshoot the bad update or just revert and wait for bugs to be fixed. If you rely on a single boot drive and storing your project files and source footage on single drives you will loose some of your work and you will be in trouble. It's guaranteed.

I hope this helps.

All depends on how good specs of your workstation are ... but lets say that you have best of the best CPU and RAM and decent GPU (that is not so important) and your rendering technique is using 90%-100%m of those resources during render then I would:
- keep my Adobe software on the same SSD as operating system
- use separate SSD for cache
- use separate drive dor input files and separate for final renders

And now if you have unlimited money resources - I would make all of those drives a good quality and fast SSD drives. But if you have to find a golden mean - all depends on what kind of work you do. For example:
a) if in your AE work you use severa high resolution raw video files and you put them throu heavy modifications using AE effects that mean that you need a quick and effective access to your source footages and your CPU will render them resonably slow so you have to put your sources into SSD (for quick access) and renders to HDD (because it renders frames so slow that your HDD will save them without any issues and slowdowns
b) if you use simpe graphics or even not to many video footages and you are sure that your CPU will render final frames really fast - then put sources on HDD and finals to SSD because if render goes fast the output drive is always a bottleneck so you have to make sure that bottleneck is as large (SSD always win on that front) as it is possible.