SanDisk 256GB Ultra microSDXC UHS-I Memory Card with Adapter - Up to 150MB/s, C10, U1, Full HD, A1, MicroSD Card - SDSQUAC-256G-GN6MA

Should be fine on the Mac using USB3, but will be much slower on iPad with Lightening..

Data Transfer

It’s known to all that Lightning cables transfer data at USB 2.0 speed, which is 480Mbps/60MBps while USB-C can handle USB 3.0 speed, with transfer speeds as fast as 5Gbps/640MBps (USB 3.1 Gen 1), or 10Gbps (USB 3.1 Gen2), and Thunderbolt 3, the superset of USB-C, is capable of 40Gbps. Although there were reports that the newer model of the Lightning connector supports a USB 3.0 host, you can only find it on some iPads. No one really knows exactly what speed Lightning can handle as Apple doesn’t release all specifications. In fact, an update on the standards of Lightning cables has not been seen in over eight years.

https://www.ipitaka.com/blogs/news/usb-c-vs-lightning-which-is-the-future