Let's run this through an analysis. From this source we find:

• 35% of the Earth is iron.
• 30% of the Earth is oxygen.
• 15% of the Earth is silicon.
• 13% of the Earth is magnesium.

That's 78%. The rest of the mass is a mix of everything else. My goal is to determine what we'd need to do to the density to achieve the results you want. But first, I need to make an assumption. You said, "double the size." As I mentioned in my comment, there's three ways to look at that. Let's assume you meant, "double the surface area." This makes the math simpler.

Twice the surface area means we need twice the volume of atmosphere and twice the gravity to hold it in place. Ouch. Our planet has 2G gravity representing twice the mass of Earth.

But it doesn't have twice the volume...

The surface of a sphere is calculated as A = 4𝛑r². Earth's surface is 510e6 Km², we want 1.02e9 Km². That's r=9,009 Km (Earth is 6,371Km) and a volume of 3.06e12 Km³ or about 3X the volume of Earth.

Now we're cooking with gas. We have 2X the mass and 3X the volume so the planet's density is 66.7% that of earth or 3.67 g/cm³.

So, I've achieved part of your request. Without changing anything other than surface gravity, we have a lower-density planet capable of holding an Earth-like atmosphere in place.

How does this affect your geology?

• Simply upsizing the Earth suggests a thicker mantle.

1. Between a thicker mantle and higher gravity, I predict your overall volcanism to be lower and your mountain building to be less. You still have tectonic plates with fissures, but less of that warmth gets to the surface. I'm thinking smoother landscape.
2. However, if we assume the same mantle thickness as Earth, the higher gravity would produce a greater tendency to shatter, meaning far more fissures and faults. Perhaps less tectonic mountain building, but potentially much more volcanic mountain building.

• A lower density means less mass-per-square-meter to do anything with. Just because you have a larger core (whether case #1 or #2 above) doesn't mean that mass is available to punch holes through the mantle or move plates around. Just as deep sea currents tend to be independent of surface sea currents, a deeper core will not translate to anything at the surface. Therefore, the physically larger core will ultimately have a lower effect on surface geology. I predict far fewer tectonic-based mountain building.
• Finally, if you really want to ratchet down the density (we need to stick with a transition metal, so our best case is scandium at 80% density of iron, which is only 35% of the mass of Earth, so the overall change is only about 7% lower density....) then we run into the problem of a lower gravity, meaning less (thinner) atmosphere and less mass to punch holes through the mantle or move plates around. It would lower the geology even more.

Please note that I'm ignoring calculations for pressure. The higher gravity means higher pressure in the outer core which means a greater chance for all kinds of mountain building. That, itself, may normalize everything such that your geology on your planet is basically identical to Earth.

Of course, your rain, wind, etc, is still eroding your mountains, so rivers, plains, gorges, canyons, they're all basically built the same way as before. Most of your actual geological shaping mechanisms won't substantially change (methinks) with the larger planet as defined.