when the screen is smaller than the graphics card resolution, the screen becomes a window, and you can scroll on the full resolution using this window.

Function 07h - Set/Get Display Start
Input: AX = 4F07h VBE Set/Get Display Start Control
(16-bit) BH = 00h Reserved and must be 00h
BL = 00h Set Display Start
= 01h Get Display Start
= 02h Schedule Display Start (Alternate)
= 03h Schedule Stereoscopic Display Start
= 04h Get Scheduled Display Start Status
= 05h Enable Stereoscopic Mode
= 06h Disable Stereoscopic Mode
= 80h Set Display Start during Vertical Retrace
= 82h Set Display Start during Vertical Retrace (Alternate)
= 83h Set Stereoscopic Display Start during Vertical Retrace
ECX = If BL=02h/82h Display Start Address in bytes
If BL=03h/83h Left Image Start Address in bytes
EDX = If BL=03h/83h Right Image Start Address in bytes
CX = If BL=00h/80h First Displayed Pixel In Scan Line
DX = If BL=00h/80h First Displayed Scan Line
Output: AX = VBE Return Status
BH = If BL=01h Reserved and will be 0
CX = If BL=01h First Displayed Pixel In Scan Line
If BL=04h 0 if flip has not occurred, not 0 if it has
DX = If BL=01h First Displayed Scan Line
Input: BH = 00h Reserved and must be 00h
(32-bit) BL = 00h Set Display Start
= 80h Set Display Start during Vertical Retrace
CX = Bits 0-15 of display start address
DX = Bits 16-31 of display start address
ES = Selector for memory mapped registers

This required function selects the pixel to be displayed in the upper left corner of the display.
This function can be used to pan and scroll around logical screens that are larger than the displayed screen.

... but VESA does not support modes what are not defined by this standard. :(

Starting with VBE version 2.0, VESA will no longer define new VESA mode numbers and it will no longer be mandatory to support these old mode numbers.

100h - 640x400 256 108h - 80 60
101h - 640x480 256 109h - 132 25
102h 6Ah 800x600 16 10Ah - 132 43
103h - 800x600 256 10Bh - 132 50
104h - 1024x768 16 10Ch - 132 60
105h - 1024x768 256
106h - 1280x1024 16
107h - 1280x1024 256
10Dh - 320x200 32K (1:5:5:5)
10Eh - 320x200 64K (5:6:5)
10Fh - 320x200 16.8M (8:8:8)
110h - 640x480 32K (1:5:5:5)
111h - 640x480 64K (5:6:5)
112h - 640x480 16.8M (8:8:8)
113h - 800x600 32K (1:5:5:5)
114h - 800x600 64K (5:6:5)
115h - 800x600 16.8M (8:8:8)
116h - 1024x768 32K (1:5:5:5)
117h - 1024x768 64K (5:6:5)
118h - 1024x768 16.8M (8:8:8)
119h - 1280x1024 32K (1:5:5:5)
11Ah - 1280x1024 64K (5:6:5)
11Bh - 1280x1024 16.8M (8:8:8)

OEM's (videocard manufacturer) who wish to add new VBE mode numbers to their implementations, must make sure that all new modes are defined with mode numbers above 0x100, However, it is highly recommended that BIOS implementations continue to support these mode numbers for compatibility with older software and add new mode numbers after the last VESA defined mode number.

It would be nice if it was possible to use any modes with any resolution using LFB or something else for example...

So, if I have a monitor with 1600x900 resolution, what mode from the list available to be most optimal for me? That's what I would like to know.

And more, maybe it's not this topic, but what about the Menuet64. From the above I assume that this OS has a 64-bit kernel but uses 16 or 32-bits VESA interface, constantly switching in (un)real mode(if it works in Protected Mode of course).