HEVC Video editing/playback - Quadro P400/600 or Geforce (1050GTX)

I hope I m in the right place for this!

Some background info: I m in the process of building a new system.
Option 1: Asus P6T6 WS (X58), X5690 or W3690, some GB of DDR3, SSD (Samsung 840PRO)
Option 2: A LGA1151 (C236 based), E3 1220/1230 v6, some GB of DDR4, same SSD as above

I d be more willing to go for option 1 - because - I m very tight on budget. Complete build for option 1 will be in the region of 400EUR vs the 800EUR+ I ll need for option 2 (I already have the mobo for option 1, brand new and several parts that will allow me to save some $$$

Obviously, I know I ll be investing 400EUR on old-spec, slower build and that option two will be faster in many respects. But since the money issue cannot be overcome and I need the system running soon, let’s stick to the point please.

My requirements: This system will be used mostly for video editing (and playback of course!). Mostly UHD (4K) but other resolutions as well. That means I need full support for anything HEVC/H265 (and H264 which is assumed). Minimal gaming.

My questions to you:

I could get my hands on a P400 or P600 for about the same money I d get a 1050GTX and 1050GTX Ti respectively. I can see Quadro support for HEVC is already in place:

And since modern pascal-based GPUs (such as P400/P600) also include support for latest DirectX and PhysX, that means playing a game is not out of question too (though as I understand, not as good as with a 1050GTX/Ti). But gaming is a low prio for this build.
Other advantages I see with a P400/P600 is that they are less power-hungry and (I m guessing) perhaps more reliable, as they are mostly intended for professional use (and not some overclocker’s kid PC).

If I go with option 1, which is more likely due to limited budget, given the fact/limitation of the P6T6 WS board of supporting only PCiE v2 (both P400/P600 are on PCiE v3), how that will affect performance? Will it work in first place? If so, will that backward compatibility mode to v2 PCiE will seriously bottleneck the card making it useless for the scope of H265 video editing that it is primarily intended for?

Is my assumption correct that, given my current requirements, that a P400/P600 will outperform a 1050? Even if both where to be plugged in a PCiE v2 slot?

So, it’s definately going to be option 1. No money for a $$$$ modern build.

Also, I managed to find answer to one of my key queries - that PCiEv2 ‘bottleneck’ imposed my the older P6T6 WS X58 board. Several sources confirm I ll be fine with not having a PCiE v3 lane to go with a modern GPU i.e.

http://www.tomshardware.co.uk/answers/id-3248140/gtx-1050-pcie.html
https://www.gamersnexus.net/guides/2488-pci-e-3-x8-vs-x16-performance-impact-on-gpus
https://linustechtips.com/main/topic/779929-gtx-1050-ti-on-pcie-20/?do=findComment&comment=9833364
https://forums.geforce.com/default/topic/1018857/geforce-1000-series/will-a-pcie-3-0-graphics-card-will-work-on-a-pcie-2-0-slot-/post/5187854/#5187854
https://www.pugetsystems.com/labs/articles/Impact-of-PCI-E-Speed-on-Gaming-Performance-518/

All of these, obviously refer to gaming performance and not video editing (which is what I need this budget build for). And all benchmarks involve GeForce based GPUs. Can i safely assume that Quadro based cards won’t be affected by the PCiE v2 limitation my mobo imposes?

Still, my question regarding the Quadro P400/P600 vs the 1050/1050Ti remains. Since I m in favour of the Quadro at the moment, and I m looking at similar prices for both, is there any reason (other than slightly better gaming performance) to go with the 1050GTX or Ti? Wouldn’t the Quadro outperform the 1050 in terms of video editing/encoding/decoding (4K HEVC and 2K)? Isn’t supposed to be build for such type of tasks?

I m also confused as to why a 1050 has 640 cuda cores - which is nearly double from what the P600 has (384)…?