as someone with that same macbook pro and a eGPU heres the low down.
while it is true thunderbolt 1 is severly limited badwidth thats only really true feeding graphics back to the internal display.
on a external display you loose about 15% or so performace over the card being in a mac pro tower or hackintosh etc.
for me thats fine i game and work on a 27" 1440p panels.
in my experiance anything above a gtx1070 or AMD equivelent is overkill as the performance doesnt gain as much as it would do to bandwidth
if you really need to use the internal monitor a "hack" i use while i want to game on the road is:
i bought a elgato HD60S usb3 capture card (needs to be the S model as it has low latency live playback)
I then set the capture cards window full screen and it shows me the video its capturing
so technically its not rendering on the main screen im just "playing" a video of whatever the GPU outputs on the main sceen.
it may sound convoluted but its basically a glorified video loopback device, downside it only captures 1080p so i really only find it useful for gaming.
As for a eGPU I went with the aorus gaming box mainly do to the fact it contains a GTX1070 (or 1080 depending on the model)
and isnt marked up that much considering how cryptomining has inflated GPU prices.
if i had a card already I would go with the Akitio Node (or node pro depending on your needs) as they appear to be the best price for what works.
as your noticing these enclosures are thunderbolt 3 so you need apple's adapter
https://www.apple.com/ca/shop/product/MMEL2AM/A/thunderbolt-3-usb-c-to-thunderbolt-2-adapter
and yes it works with thunderbolt 1 im using it right now infact
if you bootcamp you need this bootloader
https://egpu.io/egpu-setup-13x/
there are no free hacks for the bootcamp side like newer macbook pro's (believe me i looked)
if you just care about th mac side its as simple as a script in terminal and possibly drivers depending on GPU
id recommend you go to eGPU.io forums for more details
long story short, its worth it on thunderbolt 1 don't give in to the nay sayers