Straight-in versus Visual Approach (IFR Flight Plan)

[Brookfield Abused]

Straight-in (ILS or VOR Appch)?

If I am in VMC or better yet - CAVOK, I am being vectored for an ILS Apch., I have the runway in sight at the IAF and advise/request and get cleared for a "Visual Apch." - then min. Radar Vectoring Alt.(which usually only the Controller knows), OM Crossing Alt., Glide Slope and Loc. Deviations no longer play a factor (providing I remain under the Visual Stabilized Apch. criteria)? I would still be operating under my IFR Flight Plan, but have essentially advised ATC I require less of their attention, assumed more responsibility (terrain and traffic avoidance)?

On the Straight-in Apch, I was under the assumption for example RWY 18 is in use, I am cleared a 36 LOC or 36 VOR Apch and to circle for 18. To avoid this timing consuming ordeal, I have RWY 36 in sight, I can request a "Straight-in Rwy 36".... I would still be flying my IFR Flight Plan but essentially be flying a Visual on RWY 36 (most likely with a TWC).
OR
Would I just be required to request a "Visual for RWY 36"?

HOWEVER
If I am cleared an IFR Proc. which has a Proc. Turn. via the IAF, and I receive a Clearance to perform a Straight-in Apch. Then I can ignore the Proc. Turn, manoeuver, self vector myself directly to the Final Approach Course while maintain min. Altitudes or last assigned ATC vector alt.
I assume;
1. My IFR Flight Plan is still active.
2. I can be in IMC or in VMC.
3. ATC still provides AC separation.
4. ATC computer is so equipped, will monitor my terrain clearance.
5. I am still obligated to remain within Protected Airspace (ILS/VOR/NDB tolerances). Meaning for example - with full LOC deflection inside the FAF/FAP I would be required to perform a GA, UNLESS I was then truly VMC, had the RWY - lights, etc. and was Cleared a Visual?

Last one;
"Straight-in Visual Approach" - does not exist?

For me this is more a legality point of view. Essentially if I request, ATC Approves, crew reads-back, then we can legally carry out! Often SOP's/FOM's do not cover such finer points.