These sketches look great, but they can definitely be looser and more dynamic. Can you throw down a dirty sketch page that really reflects all the ideas going through your mind? Try that with pen or sharpie. Pen for the speed, sharpie for the quick dynamic effect. There’s always something interesting about the “these sketches don’t look great, but I was trying to get out all the ideas I had before I forgot them” pages.
In regards to whether or not you should try out different media right now… I don’t see why not. Just have some kind of reason for doing so, whether it be for fun, or learning intent… I used pen to stop erasing. Sharpie to be bold. I tried out pastel this past weekend because that’s what they used for automotive sketches and it looked fun! A couple years back I used a brush pen because I thought it might help improve my line control. Turns out it also made my marker work a lot more loose and energetic.
Master tools so you’re not limited in your creative expression. 
Each tool is better than another in some way, and you may need it for a reason some day… Reminds me of how anything can be a canvas. You might have to sketch on a napkin because that’s all you got and your client is right there waiting for you to sell an idea. Can you believe I iterated a print-out photoshop sketch with a folded/ripped post-it note, when in conversation with an engineer? Old-school masking effect.
Hope these thoughts are helpful in some way - I just hope you don’t get too focused about “the right way” to learn and explore. Maybe trying digital sketching this winter is a good idea. Maybe not for some reason (which I highly doubt! You will definitely learn something from it). You don’t know until you try it!