Small store with ~40 SKUs: keep a standard Shopping campaign next to PMax?

Picture a store with around 40 SKUs, a mix of cheap accessories and a few higher-ticket items. PMax is already live and pulling most of the conversions, so the question is whether a standard Shopping campaign alongside it still earns its budget. My view is yes, but only if it's tightly scoped.

PMax tends to hand the easy wins to branded search and remarketing surfaces, which hides how your products actually perform in the open auction. A Standard Shopping campaign on your best sellers, with its own bids, gives you a much cleaner read on each product. It falls apart when both campaigns chase the same queries and end up bidding against each other. With a catalog this small, I'd rather control the split myself than trust PMax to sort it out. How are others handling overlap when the feed is small?

Keeping the split manual makes sense. With 40 SKUs the overlap is mostly the same product IDs, so bids end up deciding which campaign wins. Campaign priority only settles competition between Standard Shopping campaigns, not PMax, so don't count on it to sort this one out.

I don't think bids decide which campaign wins here. When PMax and Standard Shopping both qualify for the same query and product, the auction isn't just comparing your max CPC or tROAS target. It also weighs the predicted chance of conversion for that user, and PMax often has the stronger signal on that. So a Shopping campaign can bid harder on a product and still lose impressions to PMax, which means tuning bids may be adjusting a lever that isn't doing the work.

I'd split by product instead. Put the cheap accessories PMax handles well in PMax, and keep the higher-ticket sellers in Shopping with their own budget. Custom labels in the feed make the split concrete and easy to change. After a couple of weeks, check impression share and search terms per product to see if the split is actually holding. At 40 SKUs that's manageable by hand.

Splitting by product makes sense at this size, it's easier to reason about. But before you judge how the split is performing, look at where your brand queries land. PMax still picks up branded searches on its own, so a high-ticket SKU can look weak in Shopping just because most of its brand traffic is going through PMax. Pull the search terms for both campaigns and separate branded from non-branded. If most of the brand traffic sits in PMax, you're comparing two different kinds of queries, and the per-product numbers will mislead you.

Splitting every product into branded and non-branded doesn't seem worth it to me. With around 40 SKUs you'd end up with very few conversions per cell, so you'd mostly be reading noise. PMax search term data is also less granular than Shopping's, so the split probably wouldn't be clean anyway. I'd check brand share at campaign level first. If brand queries make up a big slice of PMax conversions, that's the real problem to fix. If they're a small slice, the per-product comparison is probably fine as it is.

Checking brand share at campaign level first is the right call, and I'd make it a rule you can act on: if brand terms are more than about a fifth of PMax conversions, fix that before you read anything per product. Brand sales flatter whichever campaign they land in, so a product comparison built on them tells you about brand demand, not product performance. Below that threshold, the per-product read is usable.

For the read itself, I wouldn't lean on conversion counts at 40 SKUs, since most items won't have enough conversions to mean anything. Compare impression share, click share and cost per click for each product in both campaigns over the same window, and only call a product a winner or a loser once it has enough clicks to be stable. What counts as enough depends on your conversion rate, so set that floor yourself rather than copying someone else's number.