I live alone now but did things mostly the same when dd lived at home
Usually order my delivery for Friday afternoons
I have a delivery pass so can book 4 weeks in advance which I do by filling the "basket" with the things I get every week (bread, milk etc)
Then the day before delivery I do an update. I keep a running "note" on my phone of when deliveries are booked for, I also note any regular items I was unable to order at this time so I can add them, I also make/keep a note as the week goes on of what I want to add (usually items that are rarely ordered like laundry detergent, or items I want to try/try again) and also items I want to remove (eg if I've not used as much of something as I usually do so have plenty in)
I'm not really a meal planner but I'm trying to lose weight so trying to be more sensible/healthy in my choices. But I tend to have similar meals each week (pasta, stir fries, soup, salad, some kinda roast type thing on a Sunday, baked potato based meals lately for the weight loss)
BUT once it's arrived I'll roughly plan based on dates on perishable produce so that I'm using the shorter dated stuff first, I also put away in the fridge accordingly so that the longer dated stuff at the back
Day before delivery kitchen gets a sort out inc getting rid of/using anything that's expired/close to expiry to clear the fridge and give it a wipe down (it needs a proper clean tbh must get on that!)
I also use "nest egg" app for keeping a running inventory it lets you input expiry dates and then you can check the "alerts" page to see what needs used when at a glance and I can plan for the week based on that - also v useful for making sure I don't let rarely used tins/packets get forgotten about until they're way past expiry!
I agree with @HoppingSkipping it's good to do the update the day/night before (but watch the cut off times and allow time for "glitches") as then the stock info tends to be more up to date and you can effectively choose your own "subs" which I prefer.
That said I use Tesco who let you select which items you're ok with having substituted and which not and you can also leave specific notes for the subbed items - eg for cans of soda I put "no caffeine sugar free pls" and when they've needed to sub they've selected according to my note. Reduces returns for them to deal with too.
I occasionally need a top up order from Asda if certain items aren't available at Tesco eg recently Tesco were struggling to get fruit stocks up so I got a top up from Asda.
When this happens in order to meet the min spend and have it not mean I'm spending loads more than I normally would I'll order things from Asda which are "nice for a change" alternatives to what I get from Tesco and the following Tesco order I remove the similar equivalents from the basket. Mainly Quorn products in my case. Neither stock the full range so if I'm ordering from Asda I'll order the items from that range that Tesco don't stock, gives me a bit of variety. Some cooking sauces, salad dressings, tinned meals etc vary too so it means I have a nice variety in to choose from.
I think the nest egg app might help you plan op, takes a while to input all your "stock" in the first instance and you have to regularly keep it up to date but that only takes a few mins each Eve, but then you have a handy inventory to refer to when planning/shopping