Premixed insulin requires you to eat on a fixed schedule, and you cannot easily change your insulin dose.
Separate dosing of Lantus (long acting) and Humalog (short acting) where you inject each insulin separately (also called MDI for multi daily injections) is much more flexible. You test and adjust your basal insulin (lantus), then you dose your fast acting for each meal based on how much food / carbs/ protein you eat. You can also use your Humalog to correct for high blood sugars. Mixed insulin cannot be used to correct high blood sugars.
Strongly suggest you also ask your doctor that you should be trained to use MDI (with corrections and dosing based on carb and protein counting), not "Sliding Scale" where you simply take a fixed dose of insulin at every meal (irrespective of what you eat) and a correction in case you are high.
Thus I am strongly in favour of separate basal and bolus insulin. Book on this "think like a pancreas', "Using Insulin", Bernstein "Diabetes Solution" - there is also a Utube series called Bernstein Diabetes University that has lectures on how to use insulin and adjust diet.
Wishing you well.
please come back if you have questions.