Pontus or Venus - which inputs and cables

the enlarged pontus 15 is essentially the same dac as the venus 2 - the company is just doing some (confusing and stupid) relabeling of the models -- this company is infamous for outsmarting itself with its idiotic, constant model revisions and renaming

all things equal, i2s or aes input would be the best input if you have a streamer with a superior clock than the already quite good built in clock inside the dac (sorry i am not familiar with your smsl unit...)

otherwise use the usb input to allow the dac’s clock to control the festivities

cables matter but keep it reasonable don’t go crazy -- just buy reasonably priced well made cables of a known brand or quality, $100-200 for the cable should be enough

Assuming the DAC has a better clock I’d use USB from the A6 and most likely i2S from the SMSL.  Digital cables matter a lot so don’t skimp.  Hope this helps. 

USB from Eversolo to Denafrips. 
you will need to try AES and i2s from smsl. 
Audioquest Diamond USB or Audience StudioOne should be smooth and least digital sounding (you’re looking for that natural smooth sound to resemble your analog). 
For i2s I can’t recommend any cables…never used it. 
For AES or coax cable you can try Kimber D60. This is a well established workhorse. Should be very nice. This one is sold by Kimber Kable with full warranty and 30 days return. https://ebay.us/m/mhO0oY

I had Eversolo A6 Master (now have T8 same configuration) going USB (In-akustik USB cable-expensive but best there is according to Small Green Computer and worth the $) to DENAFRIPS Hermes DDC which then feeds Pontus II 12th DAC via I2S. I am using the Tubulus Aregentis I2S cable, also a bit costly but worth it. I am thrilled with this setup. Hope this helps…

Best of luck!