First off, the SV46P has a fixed eyepiece so it's not what you want.
I bought the SV406P 4 months ago.
TL;DR: for anyone unwilling to pay for alpha glass, the SV406P is outstanding value for money.
Eyepiece: The provided eyepiece is identical to the SV171 (8-24mm) except that it lacks filter threads.
My usage: I mount it on a Sirui VA-5 video head atop a Sirui EN-2004 tripod. I observe visually but also take pictures using my Samsung Galaxy Note 9 handheld to the eyepiece. With the eyeguard down, I get the full field of view with my eyeglasses. I raise the eyeguard 2 stops when taking pictures with the Note 9.
Visual: Sharp and CA-free even at 60x, to my eyes. Black bird against white sky, no problem.
Digiscoping: A bit of CA visible (2-3 pixels wide) if you zoom in all the way.
My other eyepieces (all Svbony):
23mm aspheric (plastic US$10 eyepiece)
9mm "redline" (Orion Expanse clone)
18mm UFF (aka APM, Orion, Meade, Altair etc).
18mm UFF is by far the highest quality of the 3, at night it is my main eyepiece. Easy to use, sharp, no astigmatism etc. I tried it during the day, very good views, 27x and 2.4 deg TFOV, but I went back to the zoom for convenience.
If you want a fixed focal length eyepiece for day use, I think the 18mm UFF is a good choice. The 15mm and 24mm UFF share the same optical design so they should be good too, just watch out for eye relief - 15mm apparently not usable with glasses, and 24mm has 29mm eye relief so without glasses there could be problems too.
9mm is very sharp but has SAEP (kidney beaning) so unusable in daytime and finicky at night. But great views of the Pleaides, Beehive Cluster, Ptolemy's Cluster etc.
23mm provides 20x and a wide field (~3 deg TFOV calculated). Eyeguard is short and fixed, eye relief is 23mm. During the day sometimes I go too near and get blackouts. Good for lower power wide views when birding at close range. Night use is fine. I don't use it much any more, the zoom is still more convenient. It is an OK eyepiece and superb value for money, but I have basically replaced it with the 18mm UFF.
Other notes:
1. SV406P eyepiece chamber is only about 25mm deep due to the sealing window (for weatherproofing and to keep the nitrogen in). Eyepieces with longer barrels will stick out and need more inward focus travel.
2. Focus travel, like all spotting scopes, is limited. Eyepieces with the focal plane too far inside the body (towards the eye) may not reach focus.
I tried a SV152 (crosshair/20mm/70 deg, same as Agena eyepiece) but it would not focus to infinity so I returned it. This eyepiece has the focal plane halfway inside the body to allow for an illuminator, so it requires a lot of inward focus travel in any telescope.
(I have been studying Ernest's eyepiece reviews on astrotalks.ru to figure out which eyepieces are likely to focus at infinity. Longer barrels can be OK if offset by focal planes that are inside the barrel, away from the eye.)
3. When pointed at a brick wall the 23mm aspheric shows only about 10-15% more bricks than the 18mm UFF instead of the 20% expected from TFOV calculations. This might be due to vignetting from the sealing window. However Ernest (of astrotalks) measured the AFOV of the 23mm at 57 deg not the claimed 62 deg, so maybe the clear aperture is indeed 27mm.
Finally, a picture says a thousand words so I attach a few pictures taken with the standard eyepiece, all handheld with my Note 9.
(pictures)
Full moon
Collared Kingfisher
Sweet Potato Bug
Common Flangetail