Here's what I see after sketching out your upgrade plan: NOW: PC1 = W10 Pro, 480W PSU, HDD (slow)
PC2 = W10 Home, 365W PSU, HDD (slow)
After the upgrade, your PCs will look like this: AFTER: 1. PC1 = W7 Home, 480W PSU, SSD (Fast)
2. PC2 = W10 Pro, 365W PSU, SSD (slow) (drive swapped from PC1)
There should be no immediate problems. The 2 PSUs that are different wattages will present no problems for you especially if they came from the HP factory with those PSUs already installed and you haven't changed them to aftermarket PSUs.
Moving the W10 Pro HDD from PC1 to PC2 should be no problems IF the 2 Motherboards are
IDENTICAL. If there are any minor differences such as the BIOS versions; e.g.: BIOS on PC2 is older or newer than BIOS on PC1, this drive/OS swap will not work! An example of this might be if PC1 BIOS = A.05; and the PC2 BIOS = A.11. If the BIOS in PC2 is the same exact version as the BIOS in PC1; for example PC1=A.11 and PC=A.11, moving the drive over is as easy as disconnecting it from PC1 and popping into PC2's case and cabling it up and turning it on. Should work. If BIOS in PC2 is older than PC1 (anything less than A.11), you could simply flash update the BIOS on PC2 to get to the same BIOS version and the swap should work.
If however, PC1 BIOS = and older BIOS, say A.05, and the PC2 BIOS= newer BIOS version, say A.11, the drive swap will NOT work in that case, since the PC1 drive being moved over to PC2 was an W10 image built on an older BIOS version than exists on PC2. This will fail.
**CAUTION: If you decided to flash update PC2 BIOS to same version as PC1 BIOS has (in that scenario), say PC2 BIOS=A.05 and you needed to flash it to A.11 to be identical with PC1 BIOS version, that would work. However, it's very critical to know that flashing your BIOS is EXTREMELY HIGH RISK,
and if you've never done it before--DON'T!! 
90% of people who attempt this without prior experience Bork their Motherboards--a Very, very expensive replacement. ($175-$1500). If you've not done it before, it's best to pay a licensed Computer Tech to do this for you. A thing I observed from drawing your plan out is than unless the existing HDD in PC2 (running W10 Home) is damaged or is smaller capacity than the HDD from PC1, why go through this HDD move here? If HDD in PC2 is Ok, why not just leave it there and stick the HDD from PC1 (old HDD) in a drawer and use for backup or stick it in PC2 as a secondary drive and use for additional storage?
The only other possible issue is that when you remove the old HDD from PC1, and insert the new SSD drive, you will need W7 install media (DVD or USB) in order to get W7 Home on the SSD. Ideally, you have factory Recovery Media (DVD or USB) for W7 in order to do this. Additionally, if PC1 came with a Microsoft COA License sticker/key for W7 Home you can install W7 Home and use that product key to activate your W7 Home on PC1 with the new SSD and W7 Home. However, if PC1 came with a different version of W7, such as W7 Pro or W7 Ultimate (1 of 9 different W7 versions), you are going to have a problem since the W7 key that came with PC1 will
NOT work with a different version of W7 (W7 Home)!!
If this is the case, you'd have to buy the correct factory Recovery Media from the aftermarket such as ebay for the matching W7 that's on the COA sticker on the case of PC1. If this isn't available in the aftermarket, you could buy the correct media directly from HP support for
$29-$99 US.
This last paragraph really describes the major problem you might have with this upgrade the way you have it laid out. Personally, I would recommend you simply use
free Image Backup Software* and Clone the W10 Pro from it's original HDD over to the new SSD drive and continue to run W10 Pro on PC1. Unless you have specific software that's not running on W10 for you, this would be much easier to accomplish. This is especially true if the software you are using
MUST USE W7 Home and cannot use any other version of W7 and the W7 version that was originally licensed to PC1 (whatever version is on the COA sticker on PC1 case) such as W7 Basic or W7 Ultimate. I've seen this requirement before, especially if you are linking to a corporate or Uni database over a web-portal connection or VPN *(
such as Outlook Exchange or Lotus Notes)*.
The other issue you should be aware of is that running the W7 Home on a new SSD will speed up that PC1 computer somewhat, but not as much as leaving W10 Pro on it. A faster OS on a newer technology drive is not as fast as a newer OS on a newer technology drive (SSD). W10 any flavor on a new SDD drive will outperform any flavor W7 on the same SSD drive. This has been well documented for 2 years now. My only conclusion is that you've left out 1 or more requirements you didn't tell us about that are software based.
Going back to W7 on PC1 is most assuredly counterproductive;
especially since W7 will be end-of-lifed by Microsoft in 2020, so that PC1 will only have 3 years left to operate before there will be no further security updates from MS, and it will be unusable for any kind of financial transactions on the Internet or secure database or E-mail over private connections (web-portal or VPN).
I have many questions on why you are doing what you are doing; as will others who read your Post. We'd appreciate you shedding some light on that.
For the free Image Backup Software we recommend*: 1. Macrium Reflect
2. Acronis TrueImage
3. EASEus Todo *We have done extensive testing with these 3 softwares on W7/W8x/W10 and they all will do the job. Let us know how you get on.
<<<BIGBEARJEDI>>> 
