Build as in body type or build as in RPG?
If it’s build as in body type, then that’s going to depend on the kind of armor he’s wearing, not the weapon he’s using. I know, it feels ironic, but it’s true. The armor is the additional weight his body is going to be lugging around and has to get used to moving quickly in, etc. Different kinds of armor create different body types.
For example, your typical martial artist will have a body type that’s similar to that of a marathon runner: long and lean. If you’re trying to identify them out of a crowd, you might accidentally pick someone who does parkour instead. Compare to someone who spends a fair amount of time wandering about in plate mail, they’ll look a little more stocky like a gymnast with a lot of muscles built up in their upper body (shoulders, back, and arms). They’ll also have thicker muscles in the neck. This isn’t because the sword is heavy, most swords were actually light weight, it’s the armor (which also isn’t that heavy, it’s cumulative over time: more weight on the body requires more stamina to keep fighting for a longer period of time and stave off fatigue).
The other thing you need to decide (though the weapon choice may have already decided it for you) is which weapon is your character’s primary? My guess would be the spear, simply because they’d always be carrying it in their hand and it’s a weapon that’s very difficult to store (you can’t put it on your hip and it’s awkward across the back), so it’s what they’d turn to first. Then, to the sword, then to the hands. The hand to hand combat they’d be most used to and use most frequently wouldn’t be punches or kicks but wrestling and grappling. The techniques you need when an opponent has gotten past your weapon’s guard and is threatening to take you to the ground. They’d be supplementary techniques for desperate situations, your character’s first instinct is going to be: always reach for the weapon. He’ll either grab for his spear or move to draw his sword, depending on what’s available. In situations where he’s feeling threatened, he’ll probably move his hand to rest on the pommel of the weapon or grip the shaft of his spear more tightly.
When writing your combat sequences focus on what the techniques are doing, not what they are. You want to craft sensations intertwined with what the characters are feeling, leave the minutiae for when they’re not in combat. The best way to prove your character knows what they’re doing is how they behave when they’re not in combat. This frees you up to keep on point during the fight sequences.
Fight Write: Your Characters Weapon is also a Character
If I were you, I’d start checking out both the Italian School and the German School of Fencing, these are the surviving schools of European sword combat styles. Also: ARMA: Association of Renaissance Martial Arts and Wiktenauer a site run by the Historical European Martial Arts Alliance and contains the worlds largest library of historical training manuals. Both groups have experts who’ve written books on the subject, I’d check those out too.
On the spear, you need to do yourself a favor and pick which style of spear combat your character is using. I’m assuming we’re talking European for sword combat, but it’s worth remembering that almost every culture throughout history across the span of globe with access to enough iron deposits had their own variation on the sword and sword combat. This is also true for the spear. The Chinese version of spear combat is wildly different from, say, the Greek, but both are effective. So, narrow your scope. If you’re doing European forms of sword combat and not say, Chinese, I’d suggest sticking with Europe but unfortunately there aren’t that many visual examples of European spear combat available. So, heh.
The Hidden Fortress by Kurosawa show cases a sequence with spear combat. Hero with Jet Li has a phenomenal combat sequence between sword and spear. 300 uses spears, obviously, I don’t know if it’s accurate to the Greeks but it’s worth throwing on the research pile. Also: the Protector of the Small quartet by Tamora Pierce has some of the best fight scenes regarding staff/spear/glaive combat and hand to hand. I’d read her entire Tortall catalog, she’s one of the few authors I feel comfortable recommending. You can tell she’s got some experience with the techniques and this series goes over some jiujutsu holds and grapples in the early books. Those will be helpful to you.
I also recommend picking up a copy of Wally Jay’s Small Circle Jujitsu and Taiji Chin Na The Seizing Art of Taijiquan by Dr. Yang, Jwing-Min. Dr. Yang, Jwing-Min also has several other books detailing both Tai Chi Chuan and Shaolin with a combat focus that might be worth a look. Both are great because they talk about concept, not just technique.