Looking for a less-beaten path

Hi all, I'm an American student spending the semester here in Wellington. I'll be heading down to the South island for two weeks in mid April, and was hoping to get some advice from locals on spots to hit. I am an experienced backpacker, having done a number of 3+ day trips, also I'm proficient at navigation, having done some bushwhacking in the Sierra Nevadas and Utah canyonlands (which are admittedly relatively devoid of bush). For my trip my partner and I are doing the Milford Track and also likely a 2 day trip out to Welcome Flats hot springs area. We'll be spending most of our time around the west coast. I'd like to find some hikes (1-3 days) that are a bit less crowded than how I expect these two routes to be, and was wondering if any of y'all had suggestions on places to hit or resources to find tracks. Aditionally, I'll be coming back around Late June, early July to do some extended (5-8 days) tramping, probably in the Nelson Lakes area, and would love suggestions on areas to hit there too! Thanks for your input and sorry if questions like this are posted very often, but the forum here is rather difficult to navigate/ search through.