You can boot multiple ISOs on one bootable flashdrive.
Download Ventoy on its official page https://www.ventoy.net/en/download.html
Extract from zip and run Ventoy2Disk.exe
Make sure your flash drive is inserted then choose it from the “Device” dropdown menu. You can try clicking the refresh button if it doesn’t show up
Click Install and follow the next steps on the program
It will ask you if you want to set it up for GPT or MBR partitions
You can choose GPT if most of your installations are for newer PCs / Laptops, or choose MBR for older systems.
After the installation is complete, you can add folders to arrange your ISO files
You can download clean Windows ISOs here: https://tb.rg-adguard.net/public.php