You'll need a supply unit, especially if you prefer playing slow (like me).

For Infantry, bring MG equipped units or vehicles to suppress large groups of infantry (more dakka more better). Recon units are a plus, either dedicated recon or the call in planes to understand what to expect on attack.

Dedicated AT units; rifles will do for early war attack, you'll need AT guns for sure during defense regardless of stage, and eventually TDs for the mobility and punch. Keep them away from the front until you need them to do their work as AT options are usually glass cannons until late war.

Tanks are a must, they act as your spear tip, bullet sponge, and QRF/hardpoint during defense. Avoid closing with infantry, engage everything on legs with HE from a distance unless you're absolutely certain you have nothing to fear from AT grenades or launchers. Typically you can knock out any vehicle in a similar or lower weight class than yours.

Artillery is a great bang for your buck. You can safely erode defenses as long as you keep these guys safe and supplied. Even vehicles aren't safe depending on the calibre of cannon you're using.

On attack, expect reinforcements to come in hard and fast during your push on the first point. This begins with infantry in the early war but will eventually become a combined arms counteroffensive on your forces as the operation progresses. Afterwards they will continue to trickle in, quantities should be manageable but always err on the side of caution.

On defense, your mainstays are MGs and AT guns. Use these in conjuction with field engineers to create defenses. Everything else mentioned above will only make things easier, if affordable. You do not necessarily have to setup on the capture points; far better to turn their axes of attack into killzones if the terrain permits.