Will there be different seats and/or positions in heaven, different levels of reward, or will we all be alike position-wise?
Not in heaven but in the Kingdom when established on earth...
Luk 19:15 And it came to pass, that when he was returned, having received the kingdom, then he commanded these servants to be called unto him, to whom he had given the money, that he might know how much every man had gained by trading.
Luk 19:16 Then came the first, saying, Lord, thy pound hath gained ten pounds.
Luk 19:17 And he said unto him, Well, thou good servant: because thou hast been faithful in a very little, have thou authority over ten cities.
Luk 19:18 And the second came, saying, Lord, thy pound hath gained five pounds.
Luk 19:19 And he said likewise to him, Be thou also over five cities.
1Co 3:9 For we are labourers together with God: ye are God's husbandry, ye are God's building.
1Co 3:10 According to the grace of God which is given unto me, as a wise masterbuilder, I have laid the foundation, and another buildeth thereon. But let every man take heed how he buildeth thereupon.
1Co 3:11 For other foundation can no man lay than that is laid, which is Jesus Christ.
1Co 3:12 Now if any man build upon this foundation gold, silver, precious stones, wood, hay, stubble;
1Co 3:13 Every man's work shall be made manifest: for the day shall declare it, because it shall be revealed by fire; and the fire shall try every man's work of what sort it is.
1Co 3:14 If any man's work abide which he hath built thereupon, he shall receive a reward.
1Co 3:15 If any man's work shall be burned, he shall suffer loss: but he himself shall be saved; yet so as by fire.
Mat 16:27 For the Son of man shall come in the glory of his Father with his angels; and then he shall reward every man according to his works.
Rev 20:12 And I saw the dead, small and great, stand before God; and the books were opened: and another book was opened, which is the book of life: and the dead were judged out of those things which were written in the books, according to their works.