WhatsApp and WeChat used to be troublesome but if you know how to do it then it's pretty straightforward.
For WhatsApp I usually do a local backup and transfer it to the USB thumbdrive, then on the new phone install WA and setup, rename the folder, restore the old WA directory, rename the msgstore-xxx.db.cryptxx to msgstore.db.cryptxx, continue the setup and all your conversations will be in tact.
For WeChat, it's even easier, Settings - Chat - Chat History Migration & Backup - Migration - Migrate to mobile/tabletWeChat, select all the chats you want to migrate, it will provide you the QR code, scan it with your WeChat from the new phone and all the conversations will be migrated.