Is it possible to change the .INI fle using the Console?

make a backup of your .ini file, always.

the proper syntax of the setini command goes as thus:

setini "parameter:category" value

so using that, to change something like doing grass shadows, it should look like this:

setini "bShadowsOnGrass=1isplay" 0

(it's a boolean value; on or off, 0 off, 1 on).

You'll need to have an understanding of which category different parameters belong to - or if you're adding a parameter that didn't exist before, know which category it should be added to.

You would probably need to do the saveini command followed by the refreshini command to see any changes -- or otherwise close/quit the game and relaunch it as some changes would require a game restart.

If you've set your SkyrimPrefs.ini or Skyrim.ini to read-only, you probably won't be able to do console commands to change it (since the game can't write to that file with it being set as read-only).
---
The Sun was born, so it shall die. As we were forged we shall return.
I know in darkness I will find you, giving up inside like me.

the above recommended command should work;;

setini "bFlyingMountFastTravelCruiseEnabled:General" 1

follow it up with:
saveini
refreshini

If it doesn't work, you can always try adding that line to your .ini with the game closed, setting it to read-only, saving it, and launching the game (the read-only step is only really there so that whatever the game might do to the .ini in the process of launching isn't kept; it could very well set that parameter to 0 each time you click "Continue From Last Save".

If nothing else, there's the mod which apparently works fine -- no reason to stop using a mod unless you are at or near the mod limit or for some reason you're unhappy with what it does (just be careful if it includes any scripts as scripts are generally saved _to your file_ and disabling mods that require them can introduce other bugs/crashes, or more noticeably random frame rate spikes).



about quotations in console commands;
usually it's for properly resolving a string or parameter that has spaces in it (like for first/last names, a handful of objects, the display name of an item, etc).

In the usage of setini's command, all examples I found via google included quotes, which makes some amount of sense since some of the parameters in the .ini have spaces; it requiring quotes is probably a catch-all to resolve that, whether the parameter you're changing has spaces or not.
---
The Sun was born, so it shall die. As we were forged we shall return.
I know in darkness I will find you, giving up inside like me.