Can I Install EA Client On Primary SSD & the Sims 4 On HDD (Internals)?

@Nuke615  Yes, you can install Sims 4 on whatever drive you like.  The EA App won't give you a choice in the matter, installing itself to C:\Program Files\Electronic Arts, but the App itself is small enough that it doesn't really matter.  Your user data will be in Documents > Electronic Arts > The Sims 4 by default, and if you want to change this, you can move all of Documents to D or create a symbolic link just for the Sims 4 data:

https://crinrict.com/blog/2020/02/moving-windows-documents-folder-to-external-drive-via-symbolic-link.html

However, I do want to point out that any quality SSD will outlive the usefulness of your new computer if you're only using it for gaming.  If you look at the documentation for the SSD you get, you'll see it rated for a lifetime of something like 50 terabytes of writes, depending on the size and who makes it.  Reads are much less stressful than writes, and after installing your games, the only writes would be the much smaller updates.

To give you something of a baseline, my gaming PC is five years old and has two SSDs, one for the OS and user files and one where I install my games and which has been full enough that I've needed to uninstall some.  They're still at 100 and 99% health, respectively.  I did pay more for the highest-quality drives, but as long as you're not getting junk, this is simply a matter of degree.  And if you do get a junk SSD, you'll want to replace it right away to avoid problems down the line.