Honest answer: when the product is identical, the product stops being the reason people buy. Price can win you a sale, but that is a race to the bottom and someone with lower overheads will always undercut you. The things that actually move the needle are what sits around the product rather than inside it.
The biggest lever with PLR is that you are allowed to change it. Most licences let you rebrand, edit and bundle. So rewrite the intro, add a chapter based on your own experience, redesign the cover, and give it a new title. Even better, bundle three related PLR items with a short video or workbook you made yourself and sell that as a package nobody else has. A five-minute recorded walkthrough of a checklist turns a commodity into something that only exists in your store. Check the licence terms before doing any of this, as some restrict resale rights or require specific attribution.
Second lever is trust. Someone landing on your site has no idea whether you will deliver the file, honour a refund, or disappear next week. A clear UK business address, your registered details if you trade as a Ltd, a plain-English refund policy (digital content has its own rules under the Consumer Rights Act 2015, so read up on the 14-day cooling-off and how it interacts with immediate downloads), and genuine reviews all do more than a nicer logo. Buyers will pay a bit more for a store that looks like it will still be there tomorrow.
Third lever is audience. A store that just lists products competes with everyone. A store with a newsletter, a blog that answers real questions, and a point of view on self-improvement competes with nobody, because people buy from you because they already know you. That takes months, not weeks, but it is the only moat that lasts with this type of product.
One practical point: if you sell to EU customers, digital services VAT rules apply from the first sale with no threshold, so look into the Non-Union OSS scheme or restrict sales to the UK until you are ready.