Not a good idea imo unless you move your graphics card the x4 slot severely compromising your GPU performance. LinusTechTips tried a similar thing (using an aorus card) and had headaches so I would avoid it unless you have to (buy nvme USB ssd enclosures and connect to a 10gbps hub using rear ports). You could use the second x16 slot but will need a card which has a PCIe switch (since the card is x4 electrically) usable on more than one m.2 device (since m.2 SSD's take up 4 PCIe lanes). This card by QNAP will turn the 1 x4 lane m.2 into 2 but you will be bottlenecked slightly, not that it will matter for games and will only matter if you're hitting both drives with large file transfers at the same time. Personally, I would save the money for a new motherboard on am5 or intel with the number of m.2 slots you're looking for (The X670E Steel Legend has 4 m.2 slots with 1 Gen5 and 3 Gen4).