The answer depends on how a shopper chooses variants and how accurately the catalogue can maintain their information. Sizes, colours and formats can be selected on a shared page or given distinct URLs. The choice must remain understandable to people and technically consistent.
Group genuine variants
Define a parent product and the attributes that really change the item sold. Each purchasable option needs an identifier, availability and, where necessary, its own price and image. Products with substantially different uses or composition should not be merged only to reduce the page count.
Choose one or several pages for the journey
A shared page often works when choices are simple and the main description stays the same. Separate pages can help when each variant has substantial unique information. In either case, a direct link must preselect the correct option with its image, price and stock. Google's ProductGroup documentation describes both patterns.
Keep URLs and data consistent
Do not create every possible parameter combination when it adds no useful difference. For a single-page model, identify one canonical URL for the group. For genuinely separate pages, each must stand on its own and match its markup. Structured data must never advertise an offer absent from the visible page.
Test difficult cases
Check an out-of-stock option, a shared link to a particular colour, browser Back and a narrow screen. Make sure the basket receives the right item. If choosing a variant changes the price or delivery time, show the difference before adding it to the basket.
Begin with three examples
Document one simple product, one with two attributes and one with an unavailable option. The catalogue preparation guide helps correct the data before applying the pattern across every product.