And these things, brethren, I transferred to myself and Apollos on your account, that in us you learn not to think above what has been written, so that you do not, each over the other, become inflated against each other.
The following summary is inductive, which takes specific points from the epistle to the Corinthians (and Galatians), and then arrives to the following general summary as probable, but not certain.
The these things refer to the divisions among the Corinthians. That is, Paul was using himself and Apollos as the figureheads of these schisms, when in fact the figureheads were Peter and John (and/or James and Jude) mentioned in 1 Cor 9:5 -- i.e, these leaders represented the "original" church in Jerusalem by whom baptism of the Holy Spirit and tongues had first appeared, and therefore were of particular import to the Corinthians. The schisms mentioned by Paul therefore centered around what-believer-was-baptized-by-what-apostle (1 Cor 1:10-17).
As was the case with the Galatians, believers familiar with the apostles in Jerusalem had arrived at Corinth and proselytized the Corinthians to follow the "real" apostles as over against Paul, who was not an "original" disciple of Jesus Christ but just some socially-ungifted parvenu to the Christian faith. (Paul drew the ironic contrast in 1 Cor 9:5 that while the "real" apostles had wives and incomes derived from their ministries, Paul and Barnabas were single and had no fixed income from anyone.) Thus the apparent schisms in Corinth focused on which apostle was the most important to follow, which had contrasted Paul's apostleship against the leaders of the Jerusalem church with emphasis on Peter as the head.
Again, like the situation with the Galatians, Paul begins in 1 Cor 1:1 that he was made an apostle not by the will of man, but by direct appointment of Jesus Christ and God the Father (not to make mention that he happened to be the "father" of the Corinthian church who had given them the "original" gospel received from Jesus Christ according to 1 Cor 4:15 and 1 Cor 9:2). Paul thus uncouples his apostleship from any legitimacy required from Peter or those in Jerusalem such as the Lord's brothers (James and Jude). Paul closed and stated that no one should be following anyone except Christ, who is THE cornerstone of the church according to 1 Cor 3:11, which draws another contradistinction to Peter, referred to in this epistle as "Cephas" (the rock).
In summary, in pure illustrative form Paul had pitted himself against Apollos as the heads of the schisms instead of Peter or John (and/or James and Jude). He did so to protect the innocent, since to do so otherwise would have increased the conflagration; that is, by illustrating the problem through Apollos and himself, Paul was not putting gasoline onto the fire, but water.
Paul had just described himself and Apollos as farmers (3:6), builders (3:10), servants and stewards (4:1).
It seems likely in following Paul's flow of thought that these are the "things" he refers back to in 4:6.