Easy conquest?

You can consult the F2P, No Grinding Path to Victory guide. And in certain Conquest recommendation threads, 𝘛𝘳𝘰𝘵𝘴𝘬𝘺 had summed up the best eras and countries to run with.

To earn medals for gens, either use Trafalgar or the older, massive Conquest grinds.
I think Fires of Revolution is recommended to farm refresh %.

As for upgrading units, why? It's not a must to upgrade them unless you want a far easier time or you plan to play without gens. Clearing missions to earn *s or buying them with a 5* trader are the only ways.

Ups - it is even not so good to upgrade top units, more than unlocking: it limits your amount of possible trainings. Just upgrades for spam-units can make sence - and remember: upgrades work only for one campaign.

If you got problems with our mods supersoldat, just post in the corresponding thread in the modification-board - we will guide You.
Important notes: You can not install a hack over the original. Only use mods that install independant. Only use mods you find here in the board as they are tested.

EW4 is one of the rare ET games that can be won without grinding. Ok, to be honest: I do 1 hour the nobility grind in Tulon to get the princess immediately. Grinding for medals is completly useless if you play the princess-game. littlecorporal made a great guide about this.

By the way, I haven't seen one working medal-grind-setup that gives notable more medals/h than normal playing.
Ony exeption: the AI-grind in Trafalgar, with minimal interaction - but even there: grinding-speed comes always out around 50-60 Medals/h.
Playing campaign for grand victory is the fastest way to get medals.

Hey which unit do you think is the best?
The Grenadier, the calvary (of any kind), or the guard? Or it's another unit?🤔

If I have to pick a single unit, it's light artillery.

Disclaimer:
I always have problems with "Who is the best" questions. Many threads ask something like this, but for me it's a childish question. There are too many aspects for a unique-answer and as you noticed, you were already reducing the selection to land units.

Erich von Manstein always has the great answer. Yes, for land units units without commander Light Artillery is one of the best units for a reasonable price - very good for countries with buffed stats. They are so vulnerable that for mass production most times single formation is the correct choice.

This does not mean that you can win a war with only Light Artillery - a pure Militia or pure Light Cavalary Army for example can crash them quickly if they are without support.

With a commander, cavalary is op (Over Powered), but if Guards Cav or the Armored Car are more usefull depends on circumstands and enemy.

PS.
Don't hesitate to create new threads if you want to discuss new questions supersoldat.

I myself spam line infantry supported by light artillery. The problem with artillery is that they have low health and movement. They need to be adequately protected and if you wait for your artilleries to reach the frontlines, it will slow your conquests.

I generally spam a few light artilleries at the frontlines and when the lines move up too far ahead, I just abandon those which remain or send them to the place which is nearest to enemy lines.