Through my experience, if you want to build muscle mass then go heavy, low reps (and I mean heavy). Stronglifts 5x5 is a great program for this. Otherwise if you focus on toning, then go light (not too light) with high reps. IMO, strength training comes first before toning down. After all strength and endurance is what helps you tone down. I've been on and off lifting for about 2 years now (I had no idea what I was doing my first year and a half...), but now I'm focusing on staying consistent with my routines, so correct me if I'm wrong in anything I say. I'm still learning, myself.
Your metabolism is what burns your fat. You want to keep your metabolism high for this (the higher your metabolism, the faster your body will break down fatty and foods). Keep your metabolism high comes from high intensity training. In this case, I would take strength training (going heavy) to be a factor of intensity training. I believe the amount of calories you eat have effect on your metabolism as well. Most people that decided go on a calorie deficit (eating lower amounts of calories than they should be) believe that the method will help "lower fat," but really you're just lowering your metabolism. However, if you're able to intertwine high intensity training alongside with a calorie deficit (slowly go down on the amount of calories per day-not a huge drop), then I believe that would help benefit in lowering your body fat. There was another thing about breaking plateaus, but I don't know much about it just yet.
As for cardio, if you want to burn fat then stick to interval training. Interval training is basically high intensity routines for a short period of time, repeated a couple of times after 30sec-1min rests. E.G. Jogging for min then jumping straight to sprinting for a 1 minute, cooldown to jogging for another minute and repeat.
Endurance training is good as well (i.e running 5 miles) as it helps boosts your endurance for when you want to start toning.
Heavy-low reps or Light-high reps is honestly a grey area. I've seen people favouring high, others favouring light, and both of them were ripped/huge. So I decided to search about it, all what I stumbled upon was articles contradicting each others.
What I've learned/believed in is, use a routine, stick to it and make sure your diet is in check. You'll make gains. Kind of reminds of the first article I read about BodyBuilding, where the guy kept emphasizing that lifting is a catalyst, and that's it's all dependent on your diet/frequency/personal will.