No, I meant I'm fine starting a new game, I just don't want to have to stop playing again because it gets laggy.
Ah ok!
Personally, I never had laggy issues ('cept the previously mentioned Club problems and some other places, and it was always because I was using an old save, or a exported old character).
I does gets slightly laggy when doing new things (i.e: starting new) because the game is loading everything. But it's a very minimal lag (like 2-3 seconds). After that seems to run fine.
On a side note, I think that fully opening the map complicates things, since the game starts to take chances of stuff (characters, events, etc) into account, so I don't run around opening everything. Usually moving around the places you actually have something to do works fine.
For example, exploring the Warehouse zone, or the centaurs zone, it's kinda pointless until you start Helena's quests and requests, so better leave that "fogged" until needed, same goes for Submission, which is a heavily loaded map.
Also, clearing map tilts keeps loading times faster. For example, finding a character that you don't have the slightlest interest, I usually just clear him up of the game, leaving the slot empty.
Clearing/adjusting races also help (in options).
For example, I don't really have interest in Caracals and Lynxes, so I just block them out. They get replaced by humans, which have much less features (for the game to load or take into account).
In my case, I usually block almost half furries (not because I hate them, but because there are lots of subspecies), which I think it's Inno's idea: not really there to have every single type, but so you can select which ones you want.
Note that some races are there just for sandboxing, but later they'll be moved to their corresponding maps (like most Club races, which are basically for a sort of "African" savannah-like map).
Adjusting their furryness "rank" also simplifies things.
Example: setting wolf-morphs to be always greater (so there's very little physical variable for the game to take into account).
Note: you could set any race to be blocked, and at any point of the game you can simply change the settings to a different race (let's say, you need/want a specific race later, you can change the options specifically to that race and have much better odds of finding it)
Basically, is better to adjust as much as you can and spend some time customizing your game, rather than just going right from the beginning.
The game is set to be generic from the beginning, and that simply brings too many options and generic variables, which lag the system.