Before I gutted my Agetec and replaced the parts with an LS-32-01 and Sanwa OSBF-30 buttons, I did play the stick with the default parts.
The Agetec’s original buttons are closer in feel to Sanwa than Seimitsu buttons. I still chose to replace them because A) the buttons on the stick I bought were noticeably scratched on the surface; B) the Sanwa buttons are still in production whereas there are no practical replacements for the Agetec buttons other than getting another Agetec and swapping its buttons for the scratched ones I had on my first Agetec!
Other than the thickness of the buttons and and the QD’s being different, the Agetec stock buttons attach like snap-in Sanwa’s and Seimitsus. You do have to cut down the “tunnel” they fit into on the interior of the Agetec to install Sanwa or Seimitsu buttons in the Agetec. Also, if you retain the original metal faceplate, you must shave the button holes wider on the faceplate because they are too narrow for the Sanwa and Seimitsu 30mm buttons to fit.