Advice request on SSD purchase and arrangement

Hi all.

I plan to buy my first SSD(s). I’ve been reading about them and it seems that a current good choice would be the Samsung 850. However I need some advice from the experienced users here regarding the specific model and arrangement.

1. Are the Pro improvements worth the price difference vs Evo?
2. Since current price differences at my local store are assumable for the following arrangements, which one makes more sense?
a) 1 x Samsung 850 (Evo or Pro) (500 or 512) GB. Would contain at least 2 OSes (main + test), Virtual Machines, Apps (Productivity, CAE) and Games.
b) 2 x Samsung 850 (Evo or Pro) (250 or 256) GB. First disk would contain OSes (plus forced Apps shared files) and Virtual Machines. Second disk would contain Apps and Games.

Both a) and b) would perform in AHCI and have in addition 2 x Seagate Barracuda 7200.14 1 TB repurposed for storage.
3. Does it make any sense in a) or b) to partition an SSD to separate Apps/Games/VMs or is this irrelevant for SSD (so everything into the correnponding OS partition in a) and single partition in second disk for option b), with proper folder arrangement)

Of course any advice on different brands or near future promising models is welcome as well.

@ Reducer:

This Forum has been designed for users, who want to optimize their already existing PC system, but not as advisor for users, who are going to purchase new PC components.
Nevertheless I will try to give you an answer:
to 1.: Yes!
to 2.: If I were you, I would buy the 512 GB Samsung 850 Pro.
to 3.: Although it may be irrelevant for SSDs to create separate partitions for the OS and other Data, I generally do it.