There are 2 types of high elbow pull to choose from.
The most common one is to sink your hand deep in the water, which generates more power, but also much more drag slowing you down. When you look around in the pool, you see 90% of swimmers using this style. I'm usually one of them.
Everyone might not be aware of the second option, or they may have tried it, and decided it's too difficult to do: it requires more flexibility - more than many older swimmers have anyway.
The other option advocated in the video below is the pro 'secret' which keeps the elbow close to the surface. Although that gives you less power, the smaller drag allows you to move faster forward in water with less wasted energy. This is the theory anyway.
You might feel pain in your shoulders when doing this. In that case I'd switch back to the easier style. Your swimming style is a result of several compromises, so it's never going to be perfect. The most important thing is to avoid injuries. We age group triathletes are fairly slow (55-59 minutes per 3800 meters) anyway, so a little added drag doesn't really matter that much to us. Better to save our precious energy for the bike and run, rather than swim a little faster and be wasted before the race really begins.