please list some of those things for us lower shooters to focus on

no need to sell you short
Depends on your ability and goals (goals like shooting 30 or shooting 100).
Coming from other games the break shot is the least natural since you don't need to play 45 degree cut shots with 20mph. Huge break with great control of CB will make your high run life much easier.
That (just practicing these cut shots with authority) will be enough to run 30-40 regularly. For regular 70+ runs your standard shots have to be 99%. So no need to devote a great portion of your time for difficult shots with 30-60% chance (though they will help you sometimes) but practicing the standard shots coming all the time in straight pool. Paying your focus on very high constant pocketing and great position.
I'd say if you can run regularly 50+ practicing actual straight pool will improve your game. With high runs of 20-30 you would be better off practicing parts of the game away from straight pool.
Deliberate practice: finding the sweet spot with drills that are hard but manageable. (Pocketing balls on the open table, get runs of 11-15 and losing position on the last 3 or missing the break ball lets spend you 75% of your time on things that don't make you better. Like you can test your level of play with straight pool but don't fool yourself, you are not actually getting better by "practicing" straight pool)
(Edit: repetition is not same as practice and repetition makes permanent, not actually better. If you spend your days playing straight pool and repeat same mistakes over and over, these mistakes gets engraved deeper in your brain. Like taking shots for granted, playing balls too thick hitting the cuchion in front of the pocket, playing lousy area position, letting off of your stroke. Spending time practicing straight pool can be a great practice and way of improvement. Depends on where your focus lies.)
Some form of brain wash drill for no rail position.
Drills for 1 rail position.
Inside English
Reading and breaking clusters
Knowing the exact path of CB.
With exception of break balls all this work will help you with all games. So basically you have to work on your fundamentals. I can post some links and examples if interested. No Idea, if the above is helpful.