Since you can not overclock the i5-10400, there is no need for a more expensive Z490 motherboard. Any lga1200 motherboard will do the job.
If, however you anticipate a upgrade to a K suffix processor like the i5-10600K in the future then a Z490 would be appropriate.
Buy only a top quality power supply.
Your psu is tier 5/6 on this list.
Credit to @Starelementpokeand @Energycore for helping out with this long-awaited refresh of the old PSU tier list by Aniallation (who previously went several months without logging in), leaving the old list in need of help. This is simply an update of the list that was flawed in creation by the P...
linustechtips.com
500w is about right, but
I have no problem overprovisioning a PSU a bit. Say 20%.
It will allow for a stronger future graphics card upgrade.
It will run cooler, quieter, and more efficiently in the middle third of it's range.
A PSU will only use the wattage demanded of it, regardless of it's max capability.
Consider a quality psu as a long term investment.
It can support several upgrades in the future since a power supply does not go obsolete quickly.
You will pay more, but consider a 650/750w seasonic focus with a 7/10 year warranty.
Here is a 650w unit with a 10 year warranty:
https://www.newegg.com/seasonic-focus-plus-650-gold-ssr-650fx-650w/p/N82E16817151186
The 750w version is only $10 more.