When it comes to lifting frequency, twice a week per muscle group works just as well as 3 times per week. You don’t make gains when you train, you make them when you recover from the training.
When it comes to intensity, strength responds best to loads between 70 and 100 percent of your 1rm. That means that you generally perform anywhere from 1 to 15 repetitions per set. When you become more advanced, you generally respond better to lower reps and higher loads.
When it comes to volume, there are some guidelines. The lower the reps, the more sets you’ll want to perform.
Regarding content, compound multi joint movements are better than isolation movements. In general, on exercise per major muscle group is sufficient volume.
When it comes to percentages, a general recommendation is to base your loads on effort rather than percentages. This means, that if a program calls for you to do sets of 5, instead of thinking about what percentage to follow you instead focus on working with a weight that allows you to complete about 5 reps and increase the level of weight when you feel able to do so.
Regarding periodization, it is often common that people who have been training for a while tend to note better gains by switching up the sets and reps on a weekly basis in a step loading approach. This means that you slightly cycle the load up and down for several weeks before you take a step back to allow recovery to take place. Once every 3-6 weeks you generally want to have an ‘’easy’’ week were you reduce the volume of your training about 50 percent.