Higher rev limit, more airflow through the head so more potential for power as the intake cam & exhaust cam separately run different lobes at different RPM - like VTEC, only each cam is activated independantly. Essentially you're taking the SR16VE & adding a 'stroker kit' to it which will give you a lot more torque than the standard 1.6L engine.
E85 was what Colm was doing with his; that was a different project altogether & that was the higher compression engine he was making for taking advantage of E85. It's a coincidence he was going to run the VE head.
Yeah there's a bit of bollocking around to make the heads fit but the likes of TJ or Colm should be able to point you in the right direction as they've each had one if memory serves.
The UK editions came with an SR20DE I remember. According to Wiki there was a JDM only Primera HP11 TE-V that came with an SR20VE.
Yeah VZRs were plenum + normal TBs, I had an N1 TB from the VZR fitted to my S14a at one stage. The Nissan Pulsar GTi-Rs had ITBs & came turbo'd. They were SR20DETs & cam transversally mounted with an AWD system. I'm not sure if they'll bolt up directly to the SR20 from the S15s, worth a look into. The alternatives include Ikeya Formula ITBs that Ken had back in the day, or again Colm has had ITBs that he had planned to put on a red-top SR so worth as ask did he complete that idea & if so how he went about it.