As for the RNG system of the this game, the random number did not change at the time of save, and when you reset it, the game begins with a specific number (it varies according to emulators etc.).
In other words,when you use a saving and reloading, you cannot reproduce the same running from there of the point compare with without using saving and reloading, but,a past random number is reset from the position that you saved ,so you can make a planned running easily.
Current RTA world record for this game is 1 hour, 9 minutes, and 49 seconds by Raikou.
http://www.speedrun.com/Digimon_World
A TAS could easily get the time down to under 1 hour by manipulating luck to end the fights quicker, and by avoiding a reset during the middle of the run (he resets the game to reset the RNG, so he can manipulate it to get metal mamemon and mamemon to appear.). You can also do a slight reroute to account for this difference, so you'll only have to pass through factorial town twice instead of 3 times.