Can I put only part of my money in Islamic products and the rest in conventional banks?

You can, and each part is handled on its own. The part you want Islamic is compared only among Islamic products, and the other part among conventional products, and each part is priced at the amount it holds, term and payout schedule. There is an important difference in the nature of the figure: Islamic banks call the return profit, and the published figure is usually an expected profit settled on the bank's actual results under the structure the bank states, so it is an estimate that can differ, not a fixed interest rate. That is why, if you add both parts' returns into one figure, that figure is an estimate at today's rate, and it can only be added at all if both parts have the same term and each is one specific product. Comparing the Islamic part's profit with the conventional part's return does not decide between them, because the two figures are different in nature. If you have a question about the religious ruling itself, ask the bank's Sharia board or a qualified fatwa authority, not a comparison tool. Ask the bank about the product's structure and how profit is computed and settled, and check each product's key-facts statement.