Where to start? There are a few threads on sail adjustment for higher winds.
You may not be racing but sailing knowledgably and well is better even for cruisers.
Generally you will go to windward better with the jib providing most of the power, and the main adding to this and balancing the boat. The jib size is appropriate for the wind speed and the main adjusted in various ways including reefing.
If your main leech was spilling wind despite the mainsheet being tight that suggests you had the traveller to windward rather than leeward.
The nett effect of having main only going upwind is that the centre of effort moves back so that gives a tendency for the boat to round up into the wind countered to doubt by your using too much rudder. To understand this imagine pushing sideways on the stern of the boat versus the bow. A balanced sail plan is the same as pushing more or less amidships so neither end turns. That requires very little helm which is faster.
You may have been sailing a bit off the wind but that would make the problem worse.
I wouldn't take too much notice of what others are doing - some being right some wrong, until you have built up a knowledge of what how and why to do things.
That will add to your enjoyment and confidence. Doesn't mean to say you spend all day tweaking the sails for the last 1/10th of a knot but does mean that when inevitably the wind gets up and you have to sail to windward you can handle it.