2018 Giant Fathom 29ER1: Fork ideas needed

My 2018 Giant Fathom is a reliable hardtail and thanks to Giants warranty I am on frame number three.

Over the last four years I have replaced other parts due to wear and tear so that all that is original are the rims, saddle, bars and forks.

Now the Suntour Axon forks are worn and have some lateral play so it’s time to open the wallet and replace them I have seen a few RockShox options up to £400.

I am thinking of going from 100mm to maybe 120mm or 140mm but I am not sure if this is a good idea, e.g. will it compromise the geometry with longer travel.

So I need ideas and recommendations please.