Hello Dd61999,
Welcome to Birdforum!
I have a Pentax PF-65EDaII and occasionally use it with a Pentax XW 3.5mm eyepiece that normally serves for astronomical viewing with other telescopes. The combination gives 111x, a .63˚ true field of view, and an exit pupil of about .6mm. While images at this magnification are sharp and without false color thanks to the ED objective, the very small exit pupil means the image is pretty dim. This is fine for viewing the moon, since it is bright. The moon subtends a .5˚ angle so it nearly fills the field of view at this power. This magnification can also be used as a "long distance microscope" to view critters like garden spiders or insects at fairly close distances in bright sunlight. At short distance, like birds at a feeder, the images are sharp and close up detail is interesting. The problem for birding or other daytime terrestrial viewing at longer distances is the wavy refraction of non-uniformly sun-heated air near the ground. While this somewhat degrades the image at low powers, it makes higher magnifications (often well below 60x) completely unusable. This is why many spotting scopes with zoom eyepieces "max out" in the 50 to 60x range. The other drawback to high magnification is the trade-off in field of view. The higher the power, the smaller the field of view, and consequently, greater difficulty in finding and keeping a bird in the scope field.
Although the Pentax XW and XL eyepieces give nice views, my most-used eyepiece for the PF65 is an adapted 2" 26mm SWA giving just 15x, a 4.5˚ field, and a bright 4.3mm exit pupil. (My preferences here may not be typical of most birders, as I'm kind of a wide field, bright view nut!)
With easy interchangeability of 1.25" barrel diameter eyepieces in the Pentax, the suggestion of "trying out" various eyepieces at a local astronomy club is a great idea. Not all astronomy eyepieces will come to infinity focus in the PF-65, but you can try out or ask here on Birdforum if you find ones of interest. You can economize by buying used eyepieces on astro-classified listings like "Cloudy Nights" (free) and Astro-Mart (fee to join). Most of my eyepieces were purchased used.
Hope this helps. - Bill