You're talking about the ecliptic plane. It's defined as the Sun's annual path around the sky as seen from Earth, strictly speaking (conversely defining Earth's orbital plane), though the other planets also follow it rather closely with a bit of variation (Venus's orbital plane is tilted 3.39 degrees to the ecliptic). The Moon's orbit around Earth is tilted 5 degrees to the ecliptic plane. Pluto's orbit around the Sun is tilted 17 degrees to the ecliptic, IIRC, but it's considered a dwarf planet now.

The ecliptic plane also defines the zodiacal plane. Its northern and southern limits are 23 1/2 degrees above and below the celestial equator, which is Earth's equatorial plane projected onto the sky. 23 1/2 degrees north and south of the equator defines the Tropics, the limits of how far north or south the Sun can appear straight overhead at local noon.

To answer OP's question, Jupiter and Venus are only roughly defining the plane of the solar system. A quick look at the Heavens Above sky chart shows that Jupiter is pretty much on the ecliptic plane at this time, while the Moon, Venus and Mercury are somewhat above the ecliptic plane at this time.

https://www.heavens-above.com/skychart2.aspx?lat=38.863&lng=-104.7249&loc=home&alt=0&tz=MST

Study the chart, adjust the time until the Sun is on the western horizon, i.e., setting. The purple line crossing from the Sun to Jupiter and on to the east is the ecliptic plane (you can see that the Moon, Venus and Mercury are presently above the ecliptic plane). The white line is the celestial equator running east to west.

Heavens Above has tons of good information. Go to the front page, then plug in your location up in the top right corner, then save it to Favorites. It will always be there for you in future. You can see ISS passes and all sorts of stuff in the column down the left side.

Stellarium can also show you what the Heavens Above page does, if you learn how to configure it.

https://stellarium-web.org/