Capacitor for TF CARD placement on PCB layout
For bulk decoupling of a SD card, I'd just put it on the same side, near the edge of the connector. Sure, you can do the math to figure out which path has more inductance/impedance -- backside + via, or top-side + some copper, but I don't think it's going to matter very much since this isn't a UHS-II / ultra-high-speed card from what looking up a TF Card was. If you have power planes, that will be your high-speed source of charge anyway.

Assumedly you're feeding this VCC from a power plane on your board anyway, so I would just place the bulk on the same side as the connector and give that cap its own vias to the power plane. Offhand I'd suggest a 0.1uF close to the pins, and then 1uF or 4.7uF somewhere close by -- caps are cheap, can't hurt (assuming you're not BOM cost sensitive).

EDIT: It's also not a bad idea to place a 0R series resistor right on the MISO pin of the connector, in case you need to add some termination in the future.