SSHD's are acting in exactly the same idea as Optane (SSD caching) + HDD.
The added cost and the unclear way in which SSHD + Optane would decide to cache makes this a poor choice. In fact, how exactly would that work? The 8GB cache on many SSHD's relies on software in the drive (and in Windows?) to place specific files (such as Windows boot files) and frequently accessed data on the SSD.
But then that's what's supposed to happen with Optane so... would Optane make the SSHD's cache pointless? Could the SSHD make things worse?
*MAIN CHOICES:
1. Optane + HDD
- superior to HDD alone
2. SSD only
- superior to Optane + HDD on average (can only cache so much so games/data not in Optane cache are on HDD thus slower than an SSD)
- best solution but also expensive with lots of games
3. SSD + HDD
- ideal balance of performance vs cost IMO
4. SSD + SSHD
- superior to SSD + HDD but hard to rate the value
*An SSHD works by caching the most frequently accessed data... thus if you play a game several times more of its data ends up in the 8GB cache. The cache will completely fill up, then if you launch a game not in the cache it will be no faster than a normal HDD.
It's not clear how well this would end up working with several games. Again, it's looking at the most frequently accessed data but would that be data that matters much?
The data a game loads initially might not end up as frequently accessed data, and the stuff that's frequently accessed might have little benefit to load times.
(SSHD vs HDD vs SSD game load tests exist however it's hard to extrapolate those results for an SSHD with many games. If you ran just one game for example then maybe most of the load data gets into the SSD cache but with 20 games who knows especially if you bounce around between games... the SSHD caching algorithm fills up the cache completely to start then monitors data access and if DATA "A" is accessed "X" number of times recently it replaces DATA "B" that hasn't been accessed much lately.)
So SSHD would at worst be no better than an HDD with similar specs, and at best similar to an SSD (so for example a game load time might be NO FASTER on the SSHD or up to maybe 3x faster). My only two concerns thus with an SSHD in this setup are:
a) added cost, and
b) potential reliability issues (are SSHD's as reliable as HDD's? I just don't know)
Summary:
My recommendation in general is simple:
SSD (Windows + apps), and
HDD (games and other).
Then consider adding another SSD specifically for games where load times justify the cost to you. A few games like PREY also have texture load issues (causing stutter) that an SSD can fix. PREY on my PC stutters on HDD but not SSD.
(you can later add an SSD and easily MOVE a Steam game over from an HDD. Very simple for most games though MODDED games are different.. for Skyrim I keep a backup copy of unmodded Skyrim so I can easily restore it... when I added the SSD I wrote down the names of every mod then removed them, deleted the game, restored the backup to the SSD, then restored the mods. )
It's POSSIBLE that there's an easier way that I'm not aware of for the mod issue.)
SKYRIM and other games may also have FREQUENT load points that an SSD can really help with. Entering buildings, dungeons and jumping to different map points are faster on an SSD... really makes a difference. I suspect an SSHD wouldn't help much but it's hard to say if the texture files would end up in the 8GB cache.
Other:
Another reason Optane + HDD might be problematic is when you choose to have your HDD's power down when not in use. I do that to avoid wearing out but primarily due to noise.. since Windows would be on the HDD anything not cached will cause it to spin up so you might click on something and then wait 5+ seconds.
Not sure in reality if that would be much of an issue as I can't test it.