Ok so I finally got my adapted N64 to start running and experimenting with my Japanese copy of the game.
I did a test with the resolutions and having jumper/expansion pack. It seems that expansion pack alone cuts a little bit of lag even on low resolution (almost unnoticeable). But the great concern is high resolution and high resolution letterbox.
For fast read all be calling Low Resolution LR, High Resolution HR, and letter box HRLB, and from this part and on all the test were made with the expansion pack.
It seems that HR and HRLB save time over LR in parts were you normally experience lag (they kinda "cut" the lag). For example: going from "gain control of Diaz" to the first door saves around 1 second in HR and HRLB.
On parts were there's normally no lag, all three methods seemed equal. To test this I used the stairs holding up (getting diaz in and out of them) for a minute and I count the nunber of times that diaz repeated the action. All three, LR, HR and HRLB had 27'ish repetitions.
So now the real talk: HR and HRLB potencially save real time (probably not game time, but you never know in this game xD), BUT they look super arkward on the screen, it almost feels like the game is cutting frames, making the game difficult and maybe even unhealthy to play.
My thoughts in the matter is that HR and HRLB should be banned for player's health sake. And btw, just having the expansion pack seems to cut very little lag even on LR.
PD: if anyone can corroborate this (although several people on the internet sais HR is unplayable) or bring similar experiences on other games with similar issues, that would be very helpful x)
Pandora.