keep it stock. VTEC-E on the VX/HX is not for power.
the ECU will throw a VTEC solenoid code if you disconnect the harness plug
honda designed it to engage at 2500rpm knowing that 90% of US highway speeds are over that rpm. i highly doubt your FE will suffer
I don't agree with the comment about vtec-e not being for power. If you've driven a VX where vtec isn't working, and then drive the same one with vtec, yeah, it's there for power-on-demand. It's needed for passing and merging.
To the OP, if you want to see how the car will be with no vtec, cause the check engine light to go on, and the car will stay out of vtec in order to protect itself. That being said, if you have a CEL on, the engine will run richer than normally in order to stay safe.
Vtec (and vtec-e) does not always engage at a certain RPM unless the throttle position is at a certain percentage. So if you accelerate very slowly but still go over 69 mph, you will stay out of vtec.
To the OP:
Don't mess with the vtec-e engagement point unless you are willing to tune the fuel maps. There is no off/on switch that can make the vtec-e motors to get better mileage. There is a lot of research into the heads of these and the tuning so that they get the amazing mileage they do. If you plan on puting that much work into it, to get a few more MPG, do it. But be ready to do a lot of work and pay a tuner and a car-dyno a lot of money to do so.
On the never-ending quest for better gas mileage...