dnd 5th – How can I add meetings in the Lost Mine of Phandelver campaign without giving too much experience to PCs?

I am reading the LMOP scenario. I was thinking of adding a few encounters if the PCs want to explore the forest or other areas of intrigue that are not taken into account in the book.

But in reality, I do not want them to earn too much XP with these devices, and since I've never done a demo, I do not know what the amounts of XP are.

The reason I care about giving them XP is that:

What I've already thought about:

In the scenario, each game is specifically rewarded by XP, so I can only give XP for scripted games, but it may seem a little disappointing for the players.

On the other hand, if I attribute to them the entirety of the experience given in the statistics blocks of the monster, one of the problems I mentioned above could result.

Given past experiences as a GM or player (especially with LMOP in particular), how can I give PC XP encounters that are not scripted without changing the scenario level too much?